Prepaid Extensions to Remote Authentication Dial-In User Service (RADIUS)
draft-lior-radius-prepaid-extensions-22
Network Working Group A. Lior
Internet-Draft Independent
Intended status: Informational P. Yegani
Expires: August 29, 2013 Juniper
K. Chowdhury
Radio Mobile Access, Inc.
H. Tschofenig
Nokia Siemens Networks
A. Pashalidis
KUL
February 25, 2013
Prepaid Extensions to Remote Authentication Dial-In User Service
(RADIUS)
draft-lior-radius-prepaid-extensions-22.txt
Abstract
This document specifies an extension to the Remote Authentication
Dial-In User Service (RADIUS) protocol that enables service providers
to charge for prepaid services. The supported charging models
supported are volume-based, duration-based, and based on one-time
events.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 29, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
1.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.1. Architectural Model . . . . . . . . . . . . . . . . . 7
1.2.2. Motivation . . . . . . . . . . . . . . . . . . . . . . 9
1.3. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 11
1.4. Example Use Case . . . . . . . . . . . . . . . . . . . . . 11
2. Supported Features . . . . . . . . . . . . . . . . . . . . . . 14
2.1. Services and Quotas . . . . . . . . . . . . . . . . . . . 14
2.2. Resource Pools . . . . . . . . . . . . . . . . . . . . . . 14
2.3. Rating Groups . . . . . . . . . . . . . . . . . . . . . . 16
2.4. Tariff Switching . . . . . . . . . . . . . . . . . . . . . 17
2.5. Support for Roaming . . . . . . . . . . . . . . . . . . . 18
2.6. Dynamic Termination . . . . . . . . . . . . . . . . . . . 19
2.7. One Time Event . . . . . . . . . . . . . . . . . . . . . . 19
2.7.1. One-Time Charging . . . . . . . . . . . . . . . . . . 19
2.7.2. Resource Consumption Query . . . . . . . . . . . . . . 20
2.7.3. Service Price Enquiry . . . . . . . . . . . . . . . . 20
2.7.4. Balance Check . . . . . . . . . . . . . . . . . . . . 21
2.7.5. Refund . . . . . . . . . . . . . . . . . . . . . . . . 21
3. Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.1. Capability Discovery . . . . . . . . . . . . . . . . . . . 22
3.2. Authentication and Authorization Operation . . . . . . . . 22
3.3. Session Start Operation . . . . . . . . . . . . . . . . . 24
3.4. Mid-Session Operation . . . . . . . . . . . . . . . . . . 24
3.5. Dynamic Operations . . . . . . . . . . . . . . . . . . . . 26
3.5.1. Unsolicited Session Termination Operation . . . . . . 26
3.5.2. Unsolicited Change of Authorization Operation . . . . 26
3.6. Termination Operation . . . . . . . . . . . . . . . . . . 27
3.7. Mobile IP Operations . . . . . . . . . . . . . . . . . . . 27
3.8. Operation Considerations for Multiple Services . . . . . . 28
3.8.1. Initial Quota Request . . . . . . . . . . . . . . . . 28
3.8.2. Quota Update . . . . . . . . . . . . . . . . . . . . . 29
3.8.3. Termination . . . . . . . . . . . . . . . . . . . . . 29
3.8.4. Dynamic Operations . . . . . . . . . . . . . . . . . . 29
3.8.5. Support for Resource Pools . . . . . . . . . . . . . . 30
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3.8.6. One-time Charging . . . . . . . . . . . . . . . . . . 30
3.8.7. Error Handling . . . . . . . . . . . . . . . . . . . . 30
3.8.8. Accounting Considerations . . . . . . . . . . . . . . 31
4. Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.1. PrePaid Accounting Capability (PPAC) Attribute . . . . . . 32
4.2. Session Termination Capability Attribute . . . . . . . . . 34
4.3. Prepaid Accounting Operation (PPAQ) Attribute . . . . . . 36
4.4. Fields . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4.5. Prepaid Tariff Switching (PTS) Attribute . . . . . . . . . 53
5. Diameter RADIUS Interoperability . . . . . . . . . . . . . . . 59
6. Security Considerations . . . . . . . . . . . . . . . . . . . 60
7. Table of Attributes . . . . . . . . . . . . . . . . . . . . . 61
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 62
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 66
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 67
10.1. Normative References . . . . . . . . . . . . . . . . . . . 67
10.2. Informative References . . . . . . . . . . . . . . . . . . 67
Appendix A. Example flows . . . . . . . . . . . . . . . . . . . . 69
A.1. A simple flow . . . . . . . . . . . . . . . . . . . . . . 69
A.2. A flow with prepaid tariff switching . . . . . . . . . . . 72
A.3. Resource pools and Rating Groups . . . . . . . . . . . . . 75
A.4. One-time charging . . . . . . . . . . . . . . . . . . . . 80
A.5. Price enquiry . . . . . . . . . . . . . . . . . . . . . . 81
A.6. Balance check . . . . . . . . . . . . . . . . . . . . . . 82
Appendix B. Translation between RADIUS Prepaid and Diameter
Credit Control . . . . . . . . . . . . . . . . . . . 84
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 93
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1. Introduction
This document specifies an extension to the RADIUS protocol that
enables service providers to perform accounting and charging in an
"online" fashion. In particular, they enable the service provider to
(a) ensure that subscriber's remaining funds suffice before the
service is delivered, and
(b) interrupt service provision when the funds are exhausted.
These capabilities are typically used in scenarios where the
subscriber maintains a prepaid account with the service provider;
hence, this extension is called the "prepaid" extension for RADIUS.
The functionality described in this document is often referred as
"online charging" in comparison to "offline charging" support
provided by RFC 2866 [RFC2866].
Note that this document does not follow the RADIUS design guidelines
outlined in RFC 6158 [RFC6158] since it predates the publication of
RFC 6158. This document documents existing implementations.
The extensions were designed with the following goals in mind:
o Make use of existing infrastructure as much as possible (including
enabling the interworking of RADIUS-based and Diameter-based
infrastructures), and thereby limit the amount of necessary
capital expenditures,
o provide the ability to rate service requests in an "online"
fashion,
o provide the ability to charge the user's account prior to service
provision,
o protect against revenue loss, i.e., to prevent an end user from
obtaining service when the available funds do not suffice,
o protect against fraud, and
o be deployable for a number of services independent of the access
network technology.
The architecture between the entities that execute the RADIUS
protocols, with the extensions defined in this document, assumes that
the rating of chargeable events does not occur in the element that
provides the service. Instead, the rating may be performed at a
dedicated server, termed the "prepaid-enabled AAA server" or simply
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"prepaid server" (PPS). Alternatively, the actual rating may occur
in an entity related to this prepaid server.
Furthermore, this document assumes that a "quota server" is available
which, through co-ordination with the rating entity and an account
balance manager, is able to provide a quota indication for a
particular user when requested. This quota server may or may not
coexist in the prepaid server.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Prepaid Client (PPC):
The entity which triggers the RADIUS message exchange, including
the prepaid extensions defined in this document. The PPC provides
the service to the users, and executes the RADIUS client which,
for the purposes of this document, is termed the "PrePaid Client"
(PPC). When the prepaid service is used the PPC collects service
event information and reports it while the services is provided to
the user. This event information is sent to the PPS using the
extensions defined in this document.
Prepaid Server (PPS):
The entity that interacts with the PPC using the RADIUS prepaid
extensions defined in this document.
Rating Entity:
This entity converts the credit that is allocated by the PPS into
a "quota". This quota is then returned to the requesting PPC via
the PPS. The rating entity may also determine that during service
provision a tariff switch will occur. In this case the rating
entity will include details of when exactly tariff switch will
occur.
Quota:
A quota denotes the amount of granted units to be consumed without
performing another credit control interaction.
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Home Network:
The network which contains the user profile and the user's prepaid
account.
Authorize-Only Access Request:
A RADIUS message of type "Access Request" (code field = 1) that
contains a "Service-Type" AVP (type = 6) with value "Authorize-
Only".
Offline Charging:
Offline charging is a process where charging information for
resource usage is collected concurrently with that resource usage.
The charging information is then passed through a chain of logical
charging functions. At the end of this process, Charging Data
Record (CDR) files are generated, which are then transferred to
the operator's billing domain for the purpose of subscriber
billing and/or inter-operator accounting (or additional functions,
e.g., statistics, at the operator's discretion). The billing
domain typically comprises post-processing systems, such as the
operator's billing system or billing mediation device. In
conclusion, offline charging is a mechanism where charging
information does not affect, in real-time, the service rendered.
[TS32240]
Online Charging:
Online charging is a process where charging information for
resource usage is collected concurrently with that resource usage
in the same fashion as in offline charging. However,
authorization for the network resource usage must be obtained
prior to the actual resource usage to occur. This authorization
is granted by the PPS upon request from the PPC. When receiving a
resource usage request, the PPS assembles the relevant charging
information and generates a charging event in real-time. The PPS
then returns an appropriate resource usage authorization. The
resource usage authorization may be limited in its scope (e.g.,
volume of data or duration), therefore the authorization may have
to be renewed from time to time as long as the resource usage
persists. Note that the charging information utilized in online
charging is not necessarily identical to the charging information
employed in offline charging. In conclusion, online charging is a
mechanism where charging information can affect, in real-time, the
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service rendered and therefore a direct interaction of the
charging mechanism with the control of resource usage is required.
[TS32240]
1.2. Overview
This section provides an overview of the prepaid charging models and
architectures, which are supported by the extensions described in
this document.
A number of models of how to charge customers for services in a
prepaid manner are supported:
o Volume-based charging (e.g., 2 Cents/KiloByte).
o Duration-based charging (e.g., 3 Cents/minute).
o Resource-based charging (e.g., 3 videos for 10 Euros)
o Event-based charging (e.g., 7 Cents/ring tone) .
This draft assumes that the user maintains a prepaid account with his
home network. This account may be used to fund multiple services,
some of which may use the extensions defined in this document, and
some may use other mechanisms. The interworking of these mechanisms
is outside the scope of this document. Similarly, the means by which
the subscriber obtains funds is also outside the scope of this
document.
1.2.1. Architectural Model
This section describes the architectural model of the protocol
extensions described in this document. Figure 1 describes the
involved entities.
The end user establishes a connection with one of possibly multiple
PPCs during service access. The selected PPC communicates with a
HAAA server (directly or indirectly via a broker network).
The interface between the HAAA and the PPS is implemented using the
RADIUS protocol together with the extensions described in this
document. However, in cases where the PPS does not implement the
RADIUS protocol, the implementation would have to map the
requirements defined in this document to a functionally equivalent
protocol.
The requesting PPC meters the consumption of the service according to
the instructions provided by the PPS. After service completion, or
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on reception of a subsequent request for service, the PPS deducts the
corresponding amount of credit from the user account. When a user
terminates an on-going service, the PPC informs the PPS with a
suitable indication about the unused portion of the allocated quota.
The PPS then refunds the user account accordingly. Note that
multiple PPSs may be deployed for reasons of redundancy and load
sharing. The system may also employ multiple rating servers.
Service
Access Device Accounting
+----------+ +---------+ Protocol +------------+
| End |<---->|+-------+|<------------>| Accounting |
| User | +->|| PCC || | Server |
| | | || ||<----+ | |
+----------+ | |+-------+| | +------------+
| +---------+ |
+----------+ | |
| End |<--+ |
| User | | +----------+
+----------+ +------->| |
Prepapid | PPS |
Protocol | |
+----------+
Figure 1: Basic Prepaid Architecture
The PPS and the accounting server in this architecture MAY be
combined. The PPC must have the ability to meter the consumption of
a prepaid data session. This metering is typically based on time
(i.e., seconds) or volume (i.e., octets).
The device running the PPC may also have "Dynamic Session
Capabilities", such as the ability to terminate a data session or to
change the filters associated with a specific data session by
processing "Disconnect" messages and "Change of Authorization"
messages as per RFC 3576 [RFC3576].
This document assumes that the PPS is used as the AAA server. There
are three types of AAA server, as follows.
The AAA server in the home network (HAAA) is responsible for
authentication of the subscriber. In addition, the HAAA communicates
with the PPS using the RADIUS protocol in order to authorize
subscribers.
This document assumes that the PPS communicates with the HAAA for the
purposes of authentication and authorisation. The PPS, in turn,
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interfaces to entities which
o keep the subscriber's account balance (balance manager),
o rate access service requests in real-time (rating engine), and
o manage quota for a particular prepaid service (quota server).
The balance manager, the rating engine and the quota server belong to
the service provider's backend infrastructure and are outside the
scope of this specification. In particular, as far as this
specification is concerned, they are assumed to exist in the PPS.
Accounting messages are not needed to deliver a prepaid service.
However, accounting messages can be used to keep the PPS up-to-date
as to what is happening with the prepaid data session.
1.2.2. Motivation
Why not use existing RADIUS attributes to construct a protocol for
prepaid scenarios? This could lead to a solution where no code has
to be modified at existing devices.
It is indeed possible to construct a solution for prepaid scenarios
using existing RADIUS attributes. The RADIUS server would send an
Access-Accept message containing a Session-Timeout(27) and include a
Termination-Action(29) in the RADIUS-request. Upon receiving the
Access-Accept message, the NAS would meter the duration of the
session and upon termination of the session the NAS would generate an
Access-Request message again. The RADIUS server would then re-
authenticate the session and reply with an Access-Accept message
indicating the amount of additional time in a Session-Timeout(27).
Alternatively, it could respond with an Access-Reject message if
there were no more resources in the user account.
Moreover, if the user terminates the session prematurely, the NAS
could indicate this in the accounting stream so that unused funds can
be returned into the prepaid user account.
Unfortunately, the above "solution" has a number of drawbacks,
including the following.
o It only supports time-based charging. The solution presented in
this document supports multiple charging metrics.
o Using accounting messages to recoup unused time may be problematic
because RADIUS accounting messages are not delivered in real-time.
A RADIUS server may store-and-forward accounting messages in
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batches. Thus, relying on accounting messages for the purposes of
prepaid may cause revenue leakage. The solution presented in this
document does not rely on Accounting packets at all. It uses
Access-Request messages, which are required to flow through any
network in real-time.
o Session-Timeout(27) is not a mandatory attribute. If a prepaid
subscriber is served by a NAS that does not adhere to Session-
Timeout then that subscriber may use the service for an
undetermined period of time.
o Termination-Action(29) presents its own issues. Firstly, the
behaviour of Termination-Action(29) is not mandatory. Secondly,
according to RFC 2865 [RFC2865], Termination-Action fires when the
provision of the service has completed. However, service should
not be terminated when negotiating additional quota, because this
should happen in a manner transparent to the subscriber. Due to
the fact that Termination-Action occurs when the service is
completed, it is unclear whether or not user experience would be
affected if this attribute would be used in a prepaid scenario.
The RADIUS server might even allocate a new IP address to the
subscriber device after a Termination-Action. Also, the RADIUS
server has no way of telling why a given Access-Request message
was generated. The RADIUS server might have to wait for the
corresponding accounting packet to determine the reason. Finally,
re-authenticating the subscriber may take too long. The solution
presented in this document allows quota replenishing to occur
without affecting user experience. No re-authentication is
required and quotas can be negotiated before the available credit
actually runs out.
o Due to the fact that the standard RADIUS attributes are not
mandatory, the correct prepaid operation is really an act of faith
on the part of the RADIUS server. If Session-Timeout(27) and/or
Termination-Action(29) are not supported, the prepaid subscriber
might be able to obtain the service for free. The solution
described in this document requires that a PPC informs the RADIUS
server, regardless of whether or not the latter supports the
prepaid extensions. The RADIUS server can then determine whether
or not service should be granted. For example, if a prepaid
subscriber is connected to a NAS that does not support prepaid,
the RADIUS server can either instruct the NAS to tunnel the
traffic to another entity in the home network (e.g., an Home
Agent) that supports prepaid, or cause it to provide only a
restricted service.
The solution presented in this document requires the support of two
mandatory and one optional attribute. Furthermore, it does not
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require a great amount of additional code at a NAS (or similar
device) that already supports time or volume-based metering. The
solution requires that RADIUS entities advertise their prepaid
capabilities in an Access-Request and that they generate an Access-
Request packet with Service-Type="Authorize-Only" in order to obtain
more quota when or before the current quota is used up. It also
requires the NAS to send an Access-Request with Service-
Type="Authorize-Only" when the session terminates in order to refund
the subscriber account.
1.3. Assumptions
This document makes the following assumptions.
o The values carried in the Service Identifiers are pre-configured
between the PPC and the PPS.
o The decision about the service rating happens at the PPS.
o The decision whether credit control requests for two services are
placed in a resource pool are made by the PPS.
o The decision which services belong to the same rating group are
pre-configured at the PPC. Once a rating group is authorized it
is not necessary to re-authorize an additional service that
belongs to the same rating group at the PPS again.
o A price enquiry is done purely for the purpose of providing AoC
for the end user, not for processing at the PPC nor to trigger any
specific actions.
1.4. Example Use Case
This section describes the sequence of events in an example RADIUS
prepaid transaction.
1. When an end host attaches to a network (for example, using IEEE
802.1X), as usual, the PPC that is servicing the subscriber uses
the AAA infrastructure in order to authenticate and authorize the
subscriber with respect to the requested service. In order to do
this, it sends a RADIUS Access-Request to the AAA server. This
Access-Request contains the subscriber's credentials and may
contain the prepaid capabilities of the PPC.
2. The authentication procedure proceeds. This may involve several
message exchanges, as it is the case with the Extensible
Authentication Protocol (EAP) [RFC2284]. Once the subscriber has
been successfully authenticated, the home AAA server determines
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that the subscriber is a prepaid subscriber and requests
authorisation from the PPS. This request MUST include the
prepaid capabilities of the serving PPC.
3. The PPS, possibly with the help of the backend infrastructure,
validates that the subscriber has a prepaid account and that the
account is active. It further validates that the PPC has the
appropriate prepaid capabilities. If all is in order, the PPS
authorises the subscriber to use the network. Otherwise it
rejects the request. The decision is sent to the AAA system in
the form of a response message. In the case of success, this
message contains attributes that indicate the allocation of a
portion of the subscriber credit. This portion is called the
"initial quota" and is expressed in units of time or volume. The
response may also include a threshold value. Note that only a
portion of the user's funds is allocated because the user may be
engaged in other services that may draw on the same account. For
example, the user may be engaged in a data session and a voice
session. Although these two services would draw from the same
account, they form separate parts of the overall system. If the
entire quota was allocated to the data session then the user
would have no more funds for a voice session.
4. The AAA system incorporates the attributes received from the PPS
into an Access-Accept message that it sends to the PPC. Note
that the AAA system is responsible for authorizing the service
whereas the prepaid system is responsible for prepaid
authorization.
5. Upon receiving the Access-Response, the PPC starts the prepaid
data session and meters the session based on time or volume, as
indicated in the message.
6. Once the consumption approaches the allocated limit (as expressed
by the threshold), the PPC will request additional quota. Re-
authorization for additional quota flows through the AAA system
to the PPS. The PPS revalidates the subscriber account and
subtracts the previously allocated quota from the current
balance. If there is remaining balance, it reauthorizes the
request with an additional quota allotment. Otherwise, the PPS
rejects the request. Note that the replenishment of the quota is
a re-authorization procedure and does not require the subscriber
to authenticate himself again.
7. Upon receiving a re-allotment of the quota, the PPC continues to
provide the requested service until the new threshold is reached.
If the request for additional quota cannot be fulfilled then the
PPC lets the subscriber use the remaining quota and terminates
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the session. Alternatively, instead of terminating the session,
the PPC may restrict service access in such a way that the
subscriber can only reach a particular web server. This web
server maybe used to allow the subscriber to replenish his
account. This restriction can also be used to allow new
subscribers to set up prepaid accounts in the first place.
8. Should the subscriber terminate the session before the quota is
exhausted, the remaining balance allotted to the session is
refunded into his account.
Note that the subscriber may have disconnected while the PPC is
waiting for the initial quota. The entire allocated quota will have
to be credited back to the subscribers account in this case. Also
note that the PPS maintains session state for the subscriber. This
state includes how much account balance was allocated during the last
quota enquiry and how much is left in the account. Therefore, it is
required that all messages about the session reach the same (and
correct) PPS.
For a simple message flow, along the lines of this use case, please
see Appendix A.
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2. Supported Features
This section describes the features that are supported by the
extensions specified in this document.
2.1. Services and Quotas
Examples of services that the user may be using are browsing the web,
participating in a VoIP conversation, watching streaming video and
downloading a ring tone. Some operators may want to distinguish
between these services and to charge them at different rates and
meters them differently. Therefore, the prepaid solution needs to be
able to distinguish services, and allocate quota to the services
using different unit types (time, volume) and allow for those quotas
to be consumed at different rates.
+---------+ +---------+ +-------+
| | 1 N | | 1 1 | |
| Session |<---------->| Service |<---------->| Quota |
| | | | | |
+---------+ +---------+ +-------+
Figure 2: Multiple services within a single session
As shown in Figure 2, a session may be associated with multiple
services. Each service is identified by a service identifier
(Service-ID). The format of the Service-ID is not in the scope of
this document. It may, for example, be expressed as a 5-tuple {i.e.,
source IP address, destination IP address, source port, destination
port, and protocol type}. Each service is associated with a quota
whereby a quota might be applicable to multiple services. An example
message flow that involves multiple services within a single session
is given in the Appendix A.
2.2. Resource Pools
When working with multiple services a new problem arises because one
service may consume its quota faster than another service. When the
user balance is close to exhaustion, a situation could arise where
one service is unable to obtain quota while another service has
plenty of quota remaining. Unless the quotas can be rebalanced, the
SAD would then have to terminate the former service. Moreover, it is
likely that each service generates a certain amount of RADIUS prepaid
traffic. In an environment with many users and charged services,
this amount of traffic may become a considerable overhead that could
lead to inefficiency.
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One method to circumvent the above situation is to use a so-called
"resource pool". Resource pools enable the allocation of resources
to multiple services of a session by allocating resources to a pool
and have services draw their quota from the pool at a rate
appropriate to that service. When the quota that has been allocated
to the pool is close to exhaustion, the entire pool (rather than
individual services) is replenished.
+-----------+
| Service-A |-----+ +--------+
+-----------+ | Ma | |
+-------->| |
| Pool |
+-------->| (1) |
+-----------+ | Mb | |
| Service-B |-----+ +--------+
+-----------+
Figure 3: Resource pool example
As shown in Figure 3, Service-A and Service-B are bound to Pool(1).
Ma and Mb are the pool multipliers (that are associated with
Service-A and Service-B respectively) that determine the rate at
which Service-A and Service-B draw from the pool.
The pool is initialized by taking the quota allocated to service n
and multiplying it by Mn. Therefore, the amount of resources
allocated to a pool is given by Poolr = Ma*Qa + Mb*Qb + . . ., where
Qn denotes the amount of quota that is allocated to service n.
Further, the pool is considered to be empty if
Poolr <= Ca*Ma + Cb*Mb + . . .,
Figure 4
where Ca and Cb are resources consumed by Service-A and Service-B
respectively.
Note that the resources assigned to the pool are not associated with
a metric. That is, Service-A can be rated at $1 per MB and Service-B
can rated at $0.10 per minute. In this case, if $5 worth of
resources are allocated for service-A to the pool and if Ma = 10,
then 50 units would be placed into the pool. If a further $5 are
allocated for service-B to the pool, then M=1 and 50 units are
deposited into the pool. The pool would then have a total sum of 100
units to be shared between the two services. The PPC would then
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mater the services such that each Mbyte used by Service-A will draw
10 units from the pool and each minute used by Service-B will draw 1
unit from the pool.
2.3. Rating Groups
A Rating Group gathers a set of services, identified by a service
identifier, and subject to the same cost and rating type (e.g., $0.1/
minute).
The rating of a service can be quite complex. While some operators
follow linear pricing models, others may wish to apply more complex
functions. For example, a service provider may wish to rate a
service such that the first N MBytes are free, then the next M Mbytes
are rated at $1 per MB and volume above (N+M) MB be rated at $0.50
per MB. Such a function could be implemented by repeated message
exchanges in the prepaid system.
To avert the need to exchange many messages while still supporting
such complex rating functions, the concept of the Rating Group was
introduced.
As shown in Figure 5, a Rating Group is associated with one or more
services and defines the rate that the services associated with the
Rating Group consume an allocated amount of quota.
+--------------+ +--------------+
+-----------+ N 1 | | M 1 | Resource Pool|
| Service-A +---------->| Rating Group |------>| or |
+-----------+ | | | Quota |
+--------------+ +--------------+
Figure 5: Rating Group
During the usage of a service that is associated with a Rating Group,
the PPC sends the ID of the Rating Group to the PPS. The PPS
authorises the Rating Group by allocating a quota to it and assign it
to a Resource Pool. When an additional service that belongs to an
already authorised Rating Group is instantiated, the PPC does not
need to re-authorize this service. This effectively means that the
PPC meters the service such that it draws from the already allocated
quota. Therefore, no RADIUS messages need to be exchanged in this
case. This limits the amount of traffic between the PPC and the PPS.
An example of a flow that uses Rating Groups is given in Appendix A.3
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2.4. Tariff Switching
Tariff is the set of parameters defining the utilization charges for
the use of a particular service.
This mechanism is useful if, for example, as shown in Figure 6,
traffic before 18:00 is rated at rate r1 and traffic after 18:00 is
rated at rate r2. The mechanism requires the PPC to report usage
before and after the switch occured.
18:00
------------------+-----------------
r1 | r2
------------------+-----------------
^ ^
|<----TSI---> |
| |
Access-Accept Access-Request
(quota allocated) (quota consumed)
Figure 6: Example of Tariff Switching
The PPC indicates support for tariff switching by setting the
appropriate bit in the PPAC. If the PPS needs to signal a tariff
switch time it will send a PTS attribute that indicates the point in
time when the switch will occur. This indication represents the
number of seconds from current time (TariffSwitchInterval TSI).
At some point after the tariff switch the PPC sends another Access-
Request, as a result of either the user having logged off or the
volume threshold being reached. The PPC reports how much volume was
used in total (in a PPAQ attribute) and how much volume was used
after the tariff switch (in a PTS VUATS subtype attribute).
In situations with multiple tariff switches, the PPS has to specify
the length of the tariff switch period using the
TimeIntervalAfterTariffSwitchUpdate (TITSU) field in the PTS
attribute, as shown in Figure 7.
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18:00 23:30
------------------+---------------------+--------------
r1 | r2 | r3
------------------+---------------------+--------------
^ ^ ^
|<----TSI---><-----------|-------->|TITSU
| |
Access-Accept Access-Request
Figure 7: Multiple Tariff Switches
When a TITSU is specified in the PTS, the PPC MUST generate an
Access-Request within the time after TSI and before TITSU expires.
Note that, typically, the PPC will be triggered by the Volume
Threshold. However, it is possible that, during period r2, resources
are not entirely consumed and, thus, the threshold is not reached.
The TITSU attribute ensures that, even in this case, the PPC will
generate the new Access-Request in good time.
For time based services, the quota is continuously consumed at the
regular rate of 60 seconds per minute. At the time when credit
resources are allocated, the server already knows how many units will
be consumed before the tariff time change and how many units will be
consumed afterward. Similarly, the server can determine the units
consumed at the before rate and the units consumed at the rate
afterward in the event that the end user closes the session before
the consumption of the allotted quota. There is no need for
additional traffic between the PPC and the PPS in the case of tariff
time changes for continuous time based service. Therefore, the
tariff change mechanism is not used for such services. For time-
based services in which the quota is not continuously consumed at a
regular rate, the tariff change mechanism described for volume and
event units may be used.
2.5. Support for Roaming
In certain networks it is essential for prepaid data services to be
available to roaming subscribers. Support for both static and
dynamic roaming models is needed. In a static roaming scenario the
subscriber connects to a foreign network which has a roaming
agreement either directly with the home network, or through a broker
network. When the subscriber logs into another foreign network, a
new login procedure has to be executed.
In a dynamic roaming scenario the subscriber may move between
networks while maintaining his connection. In such a scenario the
data session is seamlessly handed off between the networks.
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In both roaming scenarios, the subscriber always authenticates
himself to the home network. Authorization for the prepaid session
and quota replenishing occurs at the home network and more
specifically at the PPS where state is being maintained.
Roaming is challenging because a subscriber who established a prepaid
data session may move to another PPC that does not support the
prepaid extensions.
2.6. Dynamic Termination
When fraud or an error is detected, either only the affected session,
or all sessions of the affected subscriber should be immediately
terminated. Under certain conditions, the system may wish to
terminate the session in order to make sure that the user is not
charged for services it does not use.
Certain handoff procedures used in dynamic roaming scenarios require
that the system terminates the subscribers prepaid data session at a
PPC. This is the case, for example, when time-based prepaid is used
and the mobile subscriber performs a dormant handoff.
2.7. One Time Event
2.7.1. One-Time Charging
One-time charging is a mode of operation where the RADIUS prepaid
extensions are used for charging of a service that is provided
instansteneously. An example of such an event is the purchase of a
ring tone. Subscription based services can also be modeled as a one-
time event. In this case the one-time service event is the purchase
of a subscription.
For a given user, one-time charging may occur in parallel with other
charging models. For example, the subscriber may be connected to the
Internet, which is metered (based on time or volume), while he also
purchases a ring tone (a one-time-based event).
Note that it is up to the service providers to decide whether or not
the user will be charged for the download of, for example, the video
and also be charged for the data volume required to download the
video. The facilities provided by this document gives the service
provider the capability to achieve their service charging business
goals.
The PPC signals one-time charging to the PPS with an indication that
identifies the service and the units that should be debited from the
user account.
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A PPC may decide to perform one-time charging and the PPC may need to
authenticate the user before sending the relevant message to the
user's home AAA server (and to the PPS).
Note that one-time charging can also be used to credit the prepaid
account. For example, the PPC can return resources to the subscriber
by issuing a one-time charging request that includes the amount of
resources to be credited into the account.
2.7.2. Resource Consumption Query
It should be possible for the PPS to query the PPC for the current
resource consumption and to adjust the users account balance. For
example, a request to the PPS is made (e.g., a one-time charging
event), the account is depleted and resources have been allocated to
the PPC. The PPS should have the ability to query the PPC and, if it
has the spare resources, to reassign the quotas to the PPC and to the
pending request. Note that the PPS does not know resource usage
until the PPC request for more resources. This can be a long time.
In the absence of this capability the PPS can minimize the effect of
this phenomenon by allocating small quotas, a practice that results
in more message exchanges.
2.7.3. Service Price Enquiry
The PPC may need to know the price of the service event. Services
offered by application service providers whose prices are not known
in the PPC might exist. The end user might also want to get an
estimation of the price of a service event before requesting it.
A PPC issues a PPAQ to the PPS including the Requested-Action SubType
with the value set to "Price Enquiry" (2). The request includes
enough information to identify the service, namely a Service-
Identifier or a Rating-Group-Identifer.
The PPS calculates the cost of the requested service event, but it
does not perform any account balance check or credit reservation from
the account.
The estimated cost of the requested service event is returned to the
PPS with a PPAQ in the Cost-Information SubType. The PPC may
transfer the information to the end user as an advice of charge.
More information regarding the price enquiry functionality is
provided in Section 4.3.15 and in Section 4.3.17.
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2.7.4. Balance Check
The PPC may only have to verify that the end user's account balance
covers the cost of a certain service without reserving any units from
the account at the time of the inquiry. This method does not
guarantee that credit would be left when the PPC requests the
debiting of the account with a separate request.
A PPC issues a PPAQ to the PPS including the Requested-Action SubType
with the value set to "Balance Check" (1). The request includes
enough information to identify the service, namely a Service-
Identifier or a Rating-Group-Identifer.
The PPS makes the balance check, but it does not make any credit-
reservation from the account.
The result of balance check, namely "Success" (1) or "Failure" (2),
is returned to the PPC in the Check-Balance-Result SubType conveyed
in the PPAQ attribute from the PPS to the PPC.
More information regarding the balance check functionality is
provided in Section 4.3.15 and in Section 4.3.16.
2.7.5. Refund
Some services may refund service units to the end user's account; for
example, gaming services.
To initiate refunding the PPC includes the PPAQ attribute in an
Access-Request packet and the amount (as a negative value) to be
refunded is specified using the Resource Quota and Resource Quota
overflow subtypes. This functionality is similar to one-time
charging with the difference that refunding uses negative values
Information about the service need to be provided by the PPC to allow
service identification, namely the Service-ID field of the PPAQ
identifies the prepaid service.
Note that a monetary amount itself to be refunded is not provided but
rather abstract units. Based on prior out-of-band agreements between
the PPC and the PPS these abstract units are translated into a
monetary amount.
More information regarding the refund functionality is provided in
Section 3.8.6.
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3. Operations
This section contains the normative text for the prepaid extension.
3.1. Capability Discovery
The PPC initiates the authentication and authorization procedure by
sending a RADIUS Access-Request to the HAAA. Since the PPC MUST
include a PPAC attribute in the RADIUS Access-Request. The PPAC
attribute indicates to the PPS which prepaid capabilities are
possessed by the PPC. These are required in order to complete the
prepaid authorization procedure.Moreover, if the PPC supports the
Disconnect-Message or the Change-of-Authorization capabilities, then
it SHOULD include the Session Termination attribute.
In certain deployments, there may be other ways to terminate a data
session, or change authorization of an active session. For example,
some PPCs provide a session termination service via Telnet or SNMP.
In these cases, the AAA server MAY add the Dynamic-Capabilities
message to the Access-Request. Upon receiving the Change-of-
Authorization message, the AAA server would then be responsible for
terminating the session using the means that are supported by the
device.
If the authentication procedure involves multiple message exchanges
(as it is the case with EAP), the PPC MUST include the PPAC attribute
in at least the last Access-Request of the authentication procedure.
3.2. Authentication and Authorization Operation
Once the Access-Request arrives at the HAAA, the HAAA authenticates
the subscriber. If this fails, the HAAA sends an Access-Reject
message to the client. If authentication succeeds, the HAAA
determines whether or not the subscriber is a prepaid subscriber. If
the subscriber is not a prepaid subscriber, then the HAAA responds as
usual with an Access-Accept or an Access-Reject message. If the
subscriber is a prepaid subscriber then the HAAA MAY forward the
Access-Request to the PPS for further authorization.
The Access-Request contains the PPAC attribute and the Dynamic-
Capabilities attribute if one was included. The User-Name(1)
attribute MAY be set to a value that identifies the subscriber. This
attribute is used by the PPS to locate his account. For added
security, the HAAA MAY also set the User-Password(2) attribute to the
password used between the HAAA and the PPS.
The PPS locates the subscriber account and authorizes him. During
this procedure, the PPS takes into consideration the PPCs
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capabilities. Upon successful authorization, the PPS generates an
Access-Accept containing an PPAC attribute and an PPAQ attribute.
The PPAC attribute returned to the client indicates the type of
prepaid service to be provided for the session. The PPAQ attribute
includes the following information.
o The QID, which is set by the PPS to a unique value, is used to
correlate quota requests.
o Volume and/or Time quota, which is set to a value representing a
portion of the subscriber's credit.
o Time or Volume Threshold that indicates when the PPC should
request additional quota. This information is optional.
o The IP address of the serving PPS and one or more alternative
PPSs. This is used by the HAAA to route subsequent quota
replenishing messages to the appropriate PPS(s).
o A State attribute, as defined in RFC 2865 [RFC2865]. This is
necessary in order to satisfy the requirements of Section 5.44 of
RFC 2865 [RFC2865], which mandates that an Access-Request with
Service-Type="Authorize-Only" must contain a State attribute.
Since the PPC sends subsequent quota replenishment requests in the
form of such "Authorize-Only" requests, a State attribute MUST be
present in all Access-Accept messages that also carry a PPAQ
attribute.
Note: The Idle-Timeout(28) attribute can be used to trigger the
premature termination of a prepaid service, for example as a result
of inactivity.
Depending on site policies, after failed authorization, the PPS may
generate an Access-Reject in order to terminate the session
immediately. Alternatively, the PPS may generate an Access-Accept
blocking some or all of the traffic and/or redirect some or all of
the traffic to a location to a fixed server. (This feature could be
used, for example, to prompt the user to replenish their account.)
Blocking of traffic is achieved by either Filter-ID(11) or NAS-
Filter-Rule (see [RFC4849]). A description of the redirect
functionality is outside the scope of this document. The time period
before the session is blocked/redirected is specified by the Session-
Timeout(27) attribute.
Upon receiving an Access-Accept from the PPS, the HAAA appends the
usual service attributes and forward the packet to the PPC. The HAAA
SHOULD NOT overwrite any attributes already set by the PPS. If the
HAAA receives an Access-Reject message, it will simply forward the
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packet to its client. Depending on site policies, if the HAAA does
not receive an Access-Accept or an Access-Reject message from the PPS
it MAY do nothing or send an Access-Reject or an Access- Accept
message back to the PPC.
3.3. Session Start Operation
The start of the session is indicated by the arrival of an
Accounting-Request(Start) packet. The Accounting-Request (Start) MAY
be routed to the PPS such that it can confirm the initial quota
allocation.
Note that the role of the PPS is not to record accounting messages
and therefore it SHOULD NOT respond with an Accounting Response
packet. If the PPS does not receive the Accounting-Request(start)
message it will only know that the session has started upon the first
reception of a quota replenishment operation.
If the PPS does not receive indication directly (via Accounting-
Request(start)) or indirectly, it SHOULD, after some configurable
time, deduce that the session has not started. If the PPC supports
termination capabilities, the PPS SHOULD send a Disconnect Message to
the PPC as a measure to ensure that the session is indeed dead.
3.4. Mid-Session Operation
During the lifetime of a prepaid data session the PPC may request the
replenishment of the quotas using an Authorize-Only Access-Request
message. Once either the allocated quota has been exhausted or the
threshold has been reached, the PPC MUST send an Access-Request with
Service-Type(6) set to a value of "Authorize-Only" and the PPAQ
attribute.
The PPC MUST also include NAS identifiers, and Session Identifier
attributes in the Authorize-Only Access-Request. The Session
Identifier should be the same as the one used during the initial
Access-Request. For example, if the User-Name(1) attribute was used
in the Access-Request it has to be included in the Authorize-Only
Access-Request as well, especially if the User-Name(1) attribute is
used to route the Access-Request to the Home AAA server.
The Authorize-Only Access-Request MUST NOT include a User Password
and MUST NOT include a CHAP Password. In order to enable the
receiver to authenticate the message, the PPC MUST include a Message-
Authenticator(80). In order to satisfy the requirements of Section
5.44 of RFC 2865 [RFC2865], the PPC MUST also include the State
attribute. It is anticipated that the inclusion of the State
attribute will enable the PPS to map the Authorize-Only Access
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Request to the authentication context that was established when the
PPC authenticated itself at the beginning of the session. The PPC
computes the value for the Message-Authenticator and the State
attributes according to RFC 2869 [RFC2869] and RFC 2865 [RFC2865]
respectively.
When the HAAA receives an Authorize-Only Access-Request that contains
a PPAQ, it validates the message using the Message-Authenticator(80),
according to RFC 2869. If the HAAA receives an Authorize-Only
Access-Request that contains a PPAQ and either no or an invalid
Message-Authenticator(80) it SHALL silently discard the message. An
Authorize Only Access-Request message that does not contain a PPAQ is
either erroneous or belongs to another application (for example, a
Change of Authorization message [RFC3576]). In this case the
Authorize-Only Access-Request is either silently discarded or handled
by another application.
Once the Authorize-Only Access-Request message is validated, the HAAA
SHALL forward the Authorize-Only Access-Request to the appropriate
PPS. The HAAA MUST forward the Authorize-Only Access-Request to the
PPS specified in the PPAQ. The HAAA MUST add a Message-
Authenticator(80) to the message, according to RFC 2869. As with the
Access-Request message, the HAAA MAY modify the User-Name(1)
attribute such that it identifies the user to the PPS.
When the PPS receives the Authorize-Only Access-Request containing a
PPAQ attribute, it MUST validate the Message-Authenticator(80) as
described in RFC 2869. If validation fails, the PPS MUST silently
discard the message. If it receives an Authorize-Only Access-Request
message that does not contain a PPAQ, it MUST silently discard the
message.
The PPS locates the prepaid session state and uses the QID contained
within the PPAQ to detect replays. The PPS takes the most recently
allocated quota and subtracts it from the user balance. If
sufficient balance remains, the PPS authorizes the PPS and allocates
additional quota. The PPS may also calculate a new threshold value.
Upon successful re-authorization, the PPS generates an Access-Accept
containing the PPAQ attribute.
Depending on site policies, upon unsuccessful authorization, the PPS
generates an Access-Reject or an Access-Accept with Filter-Id(11) or
Ascend-Data-Filter attribute (if supported) and the Session-
Timeout(27) attribute such that the subscriber can get access to a
restricted set of locations for a short period of time. This feature
could be used to enable users to replenish their accounts, create new
accounts, or to access free content.
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Upon receiving an Access-Accept from the PPS, the HAAA forwards the
message to its client. If the HAAA receives an Access-Reject
message, it forwards the message. Depending on site policies, if the
HAAA does not receive an Access-Accept or an Access-Reject message
from the PPS it MAY do nothing or it MAY send an Access-Reject
message back to its client.
Upon receiving an Access-Accept, the PPC updates its quotas and
threshold parameters with the values contained in the PPAQ attribute.
Note that the PPS MAY update the PrePaidServer attribute(s) and these
may have to be saved as well. If the Access-Accept message contains
a Filter-Id(11), an Ascend-Data-Filter attribute, or Session
Timeout(27), the PPC SHALL restrict the subscriber session
accordingly.
3.5. Dynamic Operations
The PPS may take advantage of the dynamic capabilities that are
supported by the PPC as advertised in the Session Termination and the
PPAC attribute during the initial Access-Request. There are two
types of actions that the PPS may perform. Firstly, it may request
the session to be terminated. Secondly, it may request the
attributes associated with the session to be modified. More
specifically, it may modify a previously sent PPAQ.
Both of these actions require that the session be uniquely identified
at the PPC as described in [RFC3576].
3.5.1. Unsolicited Session Termination Operation
At anytime during a session the PPS may send a Disconnect Message in
order to terminate a session, see in [RFC3576]. Upon successful
termination of a session the PPC MUST return any unused quota to the
PPS by issuing an Authorize-Only Access-Request containing the PPAQ
which contains any unused quota and the Update-Reason set to "Remote
Forced Disconnection".
3.5.2. Unsolicited Change of Authorization Operation
At any time during the session the PPC may receive a Change of
Authorization (CoA) message. A PPS may send a new quota to either
add or to remove quota that is allocated to the service. If the
Change of Authorization contains a PPAQ then that PPAQ overrides a
previously received PPAQ. The PPS MUST NOT change the units used in
the PPAQ.
If the newly received PPAQ reduces the amount of allocated quota
beyond what is already used then the PPC accepts the new PPAQ and act
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as it normally would when the quota is used up. For example, if the
threshold is reached then is request a quota update.
3.6. Termination Operation
The termination phase is initiated when (i) the subscriber logs off,
(ii) the subscriber balance is exhausted, or (iii) when the PPC
receives a Disconnect Message.
In case the user logged off, or the PPC receives a Disconnect
Message, the PPC sends an Authorize-Only Access-Request message with
a PPAQ and Update-Reason attribute set to either "Client Service
Termination" or "Remote Forced Disconnect". This message indicates
the amount of consumed quota.
In case the currently allocated quota is exhausted, if the PPAQ
contained the Termination-Action subytype, the PPC follows the
specified action.
3.7. Mobile IP Operations
In roaming scenarios with Mobile-IP, the prepaid data session should
be maintained transparently if the HA is acting as the access device
hosting the PPC. As the subscriber device associates with a new
access service device (AP or PDSN that supports PPC capability), this
service access device sends a RADIUS Access-Request and the
subscriber is re-authenticated and reauthorized. The service access
device SHALL include the PPAC attribute in the RADIUS Access-Request.
In this manner, the procedure follows the Authentication and
Authorization procedure described earlier.
If the HA was acting as the service access device before handoff,
then the prepaid session does not undergo any change after the
handoff because the Mobile IP session is anchored at the HA and the
user's Home IP address does not change.
In the case of a wireless access point or PDSN acting as the service
access device, it is likely that the user's (care-of) IP address will
change. The prepaid session will be affected by this. In this
scenario the service access device shall send an Access-Request
message which is routed to the home network and SHALL reach the PPS
that is serving this session. The PPS correlates the new
authorization request with the existing active session and assigns a
quota to the new request. Any outstanding quota at the old service
access device SHALL be returned to the PPS if the Mobile-IP nodes (HA
and FA) support registration revocation (Mobile IPv4 only).
Specifically, the quota SHOULD be returned when the service access
device sends the Authorize-Only Access-Request with PPAQ Update-
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Reason set to either "Remote Forced Disconnect" or "Client Service
Termination". In order to trigger the sending of this last
Authorize-Only Access- Request, the PPS may issue a Disconnect
Message [3576] to the service access device.
Even if the subscriber moves to a service access device that does not
have prepaid capabilities can the prepaid data service continue.
This can be done by requesting the Home Agent (assuming it has such
capabilities) to take over the responsibilities of the service access
device (i.e. metering). This scenario will be discussed in detail in
a later version of this document.
3.8. Operation Considerations for Multiple Services
This section describes the support for multiple prepaid services on a
single PPC. Message flows illustrating the various interactions are
presented in Appendix A.
A PPC that supports prepaid operations for multi-services SHOULD set
the "Multi-Services Supported" bit in the PPAC. When working with
multi-services, we need to differentiate between the services. A
Service-Id attribute is used in the PPAQ in order to uniquely
differentiate between the services. The exact definition of the
Service-Id attribute is outside the scope of this document.
A PPAQ that contains a Service-Id is associated with that service. A
PPAQ that contains a Rating-Group-Id is associated with that Rating-
Group. A PPAQ MUST NOT contain both a Rating-Group-Id and a
Service-Id. A PPAQ that contains neither a Rating-Group-Id nor a
Service-Id then the default service is used, i.e., the "Access
Service".
3.8.1. Initial Quota Request
When operations with multiple services is desired then the PPC
requests the initial quota by sending a PPAQ containing the
Service-Id in an Authorize-Only Access-Request packet for that
service. Similarly, if the PPC supports rating groups then it may
request a quota for the rating group by sending a PPAQ containing the
Rating-Group-Id. In both cases the Update-Reason is set to "Initial-
Request". The Authorize-Only Access-Request message MAY contain more
than one PPAQ.
Upon receiving an Authorize-Only Access-Accept message containing one
or more PPAQs, the PPS allocates resources to each PPAQ. Each PPAQ
is assigned a unique QID that MUST appear in subsequent PPAQ updates
for that service or rating group. Additionally, the PPAQ MUST
contain the Service-ID or Rating-Group-Id, unless the PPAQ is the
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generic "Access Service".
3.8.2. Quota Update
Once the services start to utilize their allotted quota they will
eventually need to replenish their quotas (either the threshold is
reached or no more quota remains). In order to replenish the quota,
the PPC sends an Authorize-Only Access-Request message containing one
or more PPAQs. Each PPAQ MUST contain the appropriate QID,
Service-ID or Rating-Group-Id (or neither the Service-ID or Rating-
Group-Id if the quota replenishment is for the "Access Service").
The Update-Reason filed indicates either "Threshold reached"(3), or
"Quota reached"(4).
Upon receiving an Authorize-Only Access-Request packet with one or
more PPAQs the PPS responds with a new PPAQ for that service. The
PPAQ contains a new QID, the Service-Id or the Rating-Group-Id, and a
new QID. If the PPS does not grant additional quota for the service
it MUST include the Termination-Action subfield in the PPAQ that will
instruct the PPC to take appropriate actions.
3.8.3. Termination
When the allotted quota for a service is exhausted, the PPC shall act
in accordance with the flags set in the Termination-Action subtype.
If the Termination-Action subtype is absent then the service MUST be
terminated. If the service is to be terminated, then the PPC shall
send a PPAQ with the appropriate QID, the Service-Id, the used quota,
and the Update-Reason set to "Client Service Termination".
If the "Access Service" has terminated, then all other services must
be terminated as well. In this case the PPC MUST report on all
issued quotas for the various services. The Update-Reason field
should be set to "Access Service Terminated".
3.8.4. Dynamic Operations
Dynamic operations for multi-services are similar to dynamic
operations described for single service operations. The PPS MAY send
a COA message containing a PPAQ for an existing service instance.
The PPC matches the PPAQ with the service using the Service-ID or the
Rating-Group-Id attribute. The new quota could differ from the
previously allocated value.
A disconnect message terminates the "Access Service". As such the
PPC MUST report all unused quotas by sending an Authorize-Only Access
Request message containing a PPAQ for each active service. The
Update-Reason MAY indicate that the reason for the update.
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3.8.5. Support for Resource Pools
If the PPC supports pools as indicated by setting the "Pools
supported" bit in the PPAC then the PPS may associate a quota with a
Pool by including the Pool-Id and the Pool-Multiplier in the PPAQ.
When Resource Pools are used, the PPAQ MUST NOT use the threshold
field.
3.8.6. One-time Charging
To initiate one-time charging the PPC includes the PPAQ attribute in
an Access-Request packet. The Service-ID field of the PPAQ
identifies the prepaid service. The amount to be charged is
specified using the Resource Quota and Resource Quota overflow
subtypes. If the value specified is negative then the resources are
credited to the user account. This functionality corresponds to
refunding.
The QID subtype MUST be set to a unique value and is used by the PPS
to detect duplicates. The Update Reason field MUST be set to One-
Time Charging. Upon receiving a One-Time charge PPAQ, the RADIUS
server authenticates the user and, if successful, passes the PPAQ to
the PPS. The PPS locates the account and debits or credits it
accordingly. The PPS MUST respond to the PPS with an Access-Accept
message if successful, or an Access-Reject message otherwise.
In case of a successful operation the HAAA forwards the message to
the PPC with an Access Accept message. Since this is a one-time
charge the PPC MUST NOT allow the session to continue. Therefore,
the RADIUS server SHOULD include in the Access-Accept a Session-
Timeout set to 0. Upon receiving an Access-Accept response the PPC
SHOULD generate an Accounting Stop message.
A PPAQ used for One-Time charging MAY appear in an Authorize-Only
Access Request. This is the case when the session already exists.
The PPS responds with an Access-Accept to indicate that the user
account has been debited or an Access-Reject otherwise.
3.8.7. Error Handling
If the PPS receives a PPAQ with an invalid QID it MUST ignore that
PPAQ.
If the PPS receives a PPAQ containing a Service-Id, or a Rating-
Group-Id that it does not recognize, then it MUST ignore that PPAQ.
If the PPC receives a PPAQ containing a Service-Id, or a Rating-
Group-Id that it does not recognize, then it MUST ignore that PPAQ.
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If the PPC receives a PPAQ that contains a Pool-Id without a Pool-
Multiplier or a Pool-Multiplier without a Pool-Id it MUST ignore that
PPAQ.
3.8.8. Accounting Considerations
Although typically generated, accounting messages are not required to
deliver a prepaid data service. When generated, accounting messages
are used for auditing purposes and for billing. Accounting messages
associated with prepaid data sessions should include the PPAQ
attribute.
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4. Attributes
This section specifies the attributes that implement the RADIUS
extensions for prepaid.
4.1. PrePaid Accounting Capability (PPAC) Attribute
The PrepaidAccountingCapability (PPAC) attribute is sent in the
Access-Request message by a PPC to describe its prepaid capabilities.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Vendor-Id
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Vendor-Id (cont) | Vendor type | Vendor length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Continuation | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
The fields have the following meaning and encoding:
Type:
26 for Vendor-Specific
Length:
6 + 3 + length of SubTypes
Vendor-Id:
The Vendor-Id value for WiMAX is 24757.
Vendor type:
35 for PPAC
Vendor length:
3 + length of VALUE
Continuation:
The Continuation Field is defined as follows:
0
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0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|C|r|r|r|r|r|r|r|
+-+-+-+-+-+-+-+-+
The C-bit of the continuation field indicates
if a attribute is being fragmented. When the
C-bit is set to one '1' this indicates that
the attribute is being fragmented that is
the next VSA of the same type is to be appended
to this attribute. When the C-bit is set to zero
'0' this indicates that the next attribute is
not a fragment of this attribute.
An attribute that is not being fragmented will
have the C-bit set to '0'. An attribute that is
being fragmented will have its C-bit set to '1'
for all fragments until the last fragment, which
will have its C-bit set to '0' indicating it's
the last fragment of the attribute. The r-bits
are reserved for future use. They SHALL be set
to zero by the sender and SHALL be ignored by
the receiver.
The value of the C-bit MUST be 0.
VALUE :
The content of the AvailableInClient (AiC) SubType fields
are encoded using the data type String.
Figure 8: PPAC Attribute
The AvailableInClient (AiC) SubType is encoding as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | AvailableInClient (AiC) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AvailableInClient (AiC) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value (1)
LENGTH : 2 + 4
AvailableInClient (AiC): The bitmap is encoded as:
Value | Description
------------ -+-------------------------------------
0x00000001 | Volume metering supported
0x00000010 | Duration metering supported
0x00000100 | Resource metering supported
0x00001000 | Pools supported
0x00010000 | Rating groups supported
0x00100000 | Multi-Services supported
0x01000000 | Tariff Switch supported
0x10000000 | Reserved
Figure 9: AvailableInClient (AiC) SubType
4.2. Session Termination Capability Attribute
The Session Termination Capability attribute is included in the
RADIUS Access-Request message towards the RADIUS server to indicate
whether or not the NAS supports Dynamic Authorization.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Vendor-Id
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Vendor-Id (cont) | Vendor type | Vendor length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Continuation | String ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
The fields have the following meaning and encoding:
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Type:
26 for Vendor-Specific
Length:
6 + 3 + 4
Vendor-Id:
The Vendor-Id value for WiMAX is 24757.
Vendor type:
36 for Session Termination Capability
Vendor length:
3 + 4
Continuation:
The Continuation Field is defined as follows:
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|C|r|r|r|r|r|r|r|
+-+-+-+-+-+-+-+-+
The C-bit of the continuation field indicates
if a attribute is being fragmented. When the
C-bit is set to one '1' this indicates that
the attribute is being fragmented that is
the next VSA of the same type is to be appended
to this attribute. When the C-bit is set to zero
'0' this indicates that the next attribute is
not a fragment of this attribute.
An attribute that is not being fragmented will
have the C-bit set to '0'. An attribute that is
being fragmented will have its C-bit set to '1'
for all fragments until the last fragment, which
will have its C-bit set to '0' indicating it's
the last fragment of the attribute. The r-bits
are reserved for future use. They SHALL be set
to zero by the sender and SHALL be ignored by
the receiver.
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The value of the C-bit MUST be 0.
String:
This field is encoded as a bitmap.
Value | Description
---------------+-------------------------------------
0x00000000 | Reserved
0x00000001 | Dynamic Authorization Extensions
| (RFC 3576) is supported.
... | All further values are reserved.
Figure 10: Session Termination Capability Attribute
4.3. Prepaid Accounting Operation (PPAQ) Attribute
One or more PPAQ attributes are sent in an Access Request, Authorize-
Only Access-Request and Access-Accept message. In an Access Request
message, the PPAQ attribute is used to facilitate one-time charging
transactions. In Authorize-Only Access-Request messages it is used
for one-time charging, report usage and to request further quota. It
is also used in order to request prepaid quota for a new service
instance. In an Access-Accept message it is used in order to
allocate the (initial and subsequent) quotas.
When multiple services are supported, a PPAQ is associated with a
specific service as indicated by the presence of a Service-Id, a
Rating-Group-Id, or the "Access Service" (as indicated by the absence
of both, the Service-Id and the Rating-Group-Id).
Note: Either Volume-Quota, Time-Quota, or Resource-Quota SubTypes
MUST appear in the PPAQ attribute, except for the price enquiry
message exchange where these subtypes MUST be absent. A single PPAQ
attribute MUST NOT contain more than one Service-Id, MUST NOT contain
more than one Rating-Group-Id, and MUST NOT contain both a Service-Id
and a Rating-Group-Id. A PPAQ that does not contain a Service-ID or
a Rating-Group-Id refers to the "Access Service". A PPAQ MUST NOT
contain more than one Pool-Id. A PPAQ that contains a Pool-Id MUST
also contain a Pool-Multiplier SubType.
The PPAQ attribute, as shown in Figure 11, has a variable length
(greater than 8, encoded into one octet), and consists of a variable
number of subtypes. Unused subtypes are omitted from the message.
The following table summarizes the presence of various SubTypes in
the PPAQ attribute carried in the Access-Request and Access-Accept
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messages.
Request Accept # SubType Name
0-1(g) 0-1(m,n) 1 Quota Identifier
0-1(a,g) 0-1(a,k,n) 2 VolumeQuota
0 0-1(a,m,n) 3 VolumeThreshold
0-1(b,g) 0-1(b,k,n) 4 DurationQuota
0 0-1(b,m,n) 5 DurationThreshold
0-1(c,g) 0-1(c,k,n) 6 ResourceQuota
0 0-1(c,m,n) 7 ResourceThreshold
0-1(d,g) 0 8 Update-Reason
0-n(e,g) 0-n(e,m,n) 9 PrepaidServer
0-1(g,h,j) 0-1(m,n) 10 Service-ID
0-1(g,h,j) 0-1(m,n) 11 Rating-Group-ID
0 0-1(m,n) 12 Termination-Action
0 0-1(m,n) 13 Pool-ID
0 0-1(f,m,n) 14 Pool-Multiplier
0-1(g) 0 15 Requested-Action
0 0-1(k,m,n) 16 Check-Balance-Result
0 0-1(n) 17 Cost-Information
None of the above-listed SubTypes appears in the Access-Reject nor in
the Access-Challenge.
Notes:
(a) SHALL be present if volume based charging is used. SHALL NOT
be present otherwise. Volume- Threshold is optional.
(b) SHALL be present if duration-based charging is used. SHALL
NOT be present otherwise. Duration- Threshold is optional.
(c) SHALL be present if resource-based charging is used. SHALL
NOT be present otherwise. Resource- Threshold is optional.
(d) SHALL be present in an Authorize-Only Access-Request.
(e) MAY be present in an Access-Accept. If present in Access
Accept it SHALL be present in Access- Request (except for the
first Access-Request).
(f) Pool-Multiplier SHALL be present when Pool-ID is present
otherwise Pool-Multiplier SHALL NOT be present in the PPAQ.
(g) If Requested-Action is present then Service-ID SHALL also be
present and all other attributes SHALL NOT be present.
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(h) PPAQ SHALL NOT contain both a Service-ID and a
Rating-Group-ID.
(j) A PPAQ that does not contain a Service-ID or a Rating-Group-Id
refers to the "Access Service"(ISF).
(k) If Balance-Check-Result is present and set to 0 then either
Volume-Quota, Duration-Quota or Resource- Quota SHALL be present.
(m) If Balance-Check-Result is present then Service-ID SHALL also
be present and other attributes (tagged with m) SHALL NOT be
present.
(n) The PPAQ in which a Cost-Information occurs SHALL NOT include
a Quota-Identifier, because no quota is actually reserved by the
PPS. The Service-ID SHALL be present with the Cost-Information
for that Service-ID may not be present if the Cost-Information
cannot be provided. All other attribute SHALL not appear.
In the following subsections the various subtypes of the PPAQ
attribute are specified.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Vendor-Id
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Vendor-Id (cont) | Vendor type | Vendor length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Continuation | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
The fields have the following meaning and encoding:
Type:
26 for Vendor-Specific
Length:
6 + 3 + length of SubTypes
Vendor-Id:
The Vendor-Id value for WiMAX is 24757.
Vendor type:
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37 for PPAQ
Vendor length:
3 + length of SubTypes
Continuation:
The Continuation Field is defined as follows:
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|C|r|r|r|r|r|r|r|
+-+-+-+-+-+-+-+-+
The C-bit of the continuation field indicates
if a attribute is being fragmented. When the
C-bit is set to one '1' this indicates that
the attribute is being fragmented that is
the next VSA of the same type is to be appended
to this attribute. When the C-bit is set to zero
'0' this indicates that the next attribute is
not a fragment of this attribute.
An attribute that is not being fragmented will
have the C-bit set to '0'. An attribute that is
being fragmented will have its C-bit set to '1'
for all fragments until the last fragment, which
will have its C-bit set to '0' indicating it's
the last fragment of the attribute. The r-bits
are reserved for future use. They SHALL be set
to zero by the sender and SHALL be ignored by
the receiver.
The value of the C-bit MAY be 0 or 1.
VALUE:
Data type String
Each SubType is then encoded in the following style:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
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SubType :
Contains an 8 bit unsigned integer.
LENGTH :
Contains an 8 bit unsigned integer.
The value of the LENGTH field is calculated as the length of the
VALUE field plus two octets (one octet for the length of the
SubType field and another octet for the length of the LENGTH
field).
Figure 11: PPAQ Attribute Encoding Style
4.3.1. Quota Identifier (QID) SubType
The Quota Identifier (QID) is generated by the PPS and subsequently
returned in a PPAQ->QID subtype from the PPC to the PPS. This field
has the semantic of a transaction identifier and therefore changes
with every transaction initiated by the PPS to the PPC.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VALUE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(1)
LENGTH : 2 + length of VALUE field.
VALUE : Data type String
Quota Identifier (QID) SubType
4.3.2. VolumeQuota SubType
TVolumeQuota SubType is only present when volume-based charging is
used. In a RADIUS Access-Accept message (PPS to PPC direction), it
indicates the volume (in octets) allocated for the session by the
PPS. In a RADIUS Authorize-Only Access-Request message (PPC to PPS
direction), it indicates the totally used volume (in octets) for both
inbound and outbound traffic. The Exponent Field, if present, MUST
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NOT encode a negative number or zero.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(2)
LENGTH : 2 + (8 or 12)
VALUE : Data type String
The content of the VALUE field either contains the
Value-Digits Field (8 octets long) or the Value-Digits Field
plus the Exponent Field (12 octets long).
VolumeQuota SubType
4.3.3. VolumeThreshold SubType
The value of the type field of the VolumeThreshold SubType is TBD and
its length is 10 or 14 octets. This SubType is optionally present if
the VolumeQuota is present in a RADIUS Access-Accept message (PPS to
PPC direction). It is generated by the PPS and indicates the volume
(in octets) that has to be consumed before a new quota is requested.
This threshold MUST NOT be larger than the VolumeQuota. The Exponent
Field, if present, MUST NOT encode a negative number or zero.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(3)
LENGTH : 2 + (8 or 12)
VALUE : Data type String
The content of the VALUE field either contains the
Value-Digits Field (8 octets long) or the Value-Digits
SubType plus the Exponent Field 12 octets long).
VolumeThreshold SubType
4.3.4. DurationQuota SubType
The optional DurationQuota SubType is only present if duration-based
charging is used. In a RADIUS Access-Accept message (PPS to PPC
direction), it indicates the duration (in seconds) allocated for the
session by the PPS. In a RADIUS Access-Request message (PPC to PPS
direction), it indicates the total duration (in seconds) since the
start of the accounting session related to the QID subtype of the
PPAQ attribute in which it occurs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VALUE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(4)
LENGTH : 2 + 4
VALUE : Data type string.
The content of this field contains a 32-bit unsigned integer
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(with the values 0 to +4,294,967,295).
DurationQuota SubType
4.3.5. DurationThreshold SubType
The DurationThreshold SubType is optionally present if the
DurationQuota is present in a RADIUS Access-Accept message (PPS to
PPC direction). It represents the duration (in seconds) after which
new quota should be requested. This threshold MUST NOT be larger
than the DurationQuota SubType.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VALUE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(5)
LENGTH : 2 + 4
VALUE : Data type string.
The content of this field contains a 32-bit unsigned integer
(with the values 0 to +4,294,967,295).
DurationThreshold SubType
4.3.6. ResourceQuota SubType
The optional ResourceQuota SubType is only present if resource-based
or one-time charging is used. In the RADIUS Access-Accept message
(PPS to PPC direction) it indicates the resources allocated for the
session by the PPS. In RADIUS Authorize-Only Access-Request message
(PPC to PPS direction), it indicates the resources used in total,
including both incoming and outgoing chargeable traffic. In one-time
charging scenarios, the subtype represents the number of units to
charge the user. The attribute consists of a Value-Digits Field and
optionally an Exponent Field (as indicated by the length field).
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(6)
LENGTH : 2 + (8 or 12)
VALUE : Data type String
The content of the VALUE field either contains the
Value-Digits Field (8 octets long) or the Value-Digits Field
plus the Exponent Field (12 octets long).
ResourceQuota SubType
4.3.7. ResourceThreshold SubType
The semantic of the ResourceThreshold SubType follow those of the
VolumeThreshold and DurationThreshold SubType.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(7)
LENGTH : 2 + (8 or 12)
VALUE : Data type String
The content of the VALUE field either contains the
Value-Digits Field (8 octets long) or the Value-Digits Field
plus the Exponent Field (12 octets long).
ResourceThreshold SubType
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4.3.8. Update-Reason SubType
The Update-Reason SubType is present in a RADIUS Access-Request
message (PPC to PPS direction) and indicates the reason for
initiating the quota update operation. Update reasons (6), (7), (8)
and (9) indicate that the associated resources are released at the
PPC side, and that therefore the PPS MUST NOT allocate a new quota in
the RADIUS Access-Accept message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(8)
LENGTH : 2 + 1
VALUE : Data type string
This field contains a byte
(with the values 0 to 255).
Update-Reason SubType
The following values for the Update-Reason SubType are defined:
Value | Description
-------------+--------------------------------------
0 | Reserved
1 | Pre-initialization
2 | Initial Request
3 | Threshold Reached
4 | Quota Reached
5 | TITSU Approaching
6 | Remote Forced Disconnect
7 | Client Service Termination
8 | "Access Service" Terminated
9 | Service not established
10 | One-Time Charging
11...255 | **Available for IANA registration**
Figure 12: Values for Update-Reason SubType
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4.3.9. PrepaidServer SubType
The optional PrepaidServer SubType indicates the address of the
serving PPS. If present, the Home RADIUS server uses this address to
route the message to the serving PPS. Multiple instances of this
subtype MAY be present in a single PPAQ attribute.
If present in the PrepaidServer SubType of an incoming RADIUS Access-
Accept message, the PPC returns this SubType back without modifying
it in the subsequent RADIUS Access-Request message. If multiple
values are present, the PPC MUST NOT change their order.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | Address ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(9)
LENGTH : 2 + (4 or 16)
Address : Data type String
For IPv4, the Address field is 4 octets based on the encoding of
the NAS-IP-Address defined in RFC 2138. For IPv6, the Address
field is 16 octets long.
PrepaidServer SubType
4.3.10. Service-ID SubType
The Service-ID SubType is handled as an opaque string that uniquely
describes the service instance for which prepaid metering should be
applied.
A Service-Id could be an IP 5-tuple (source address, source port,
destination address, destination port, protocol). If a Service-ID
SubType is present in the PPAQ, the entire PPAQ attribute refers to
that service. If a PPAQ attribute does not contain a Service-Id or
Rating-Group-ID, then the PPAQ attribute refers to the "Access
Service".
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | Service ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(10)
LENGTH : 2 + length (Service)
Service : Data type String
Service-ID SubType
4.3.11. Rating-Group-ID SubType
The Rating-Group-ID SubType indicates that this PPAQ attribute is
associated with resources allocated to a Rating Group with the
corresponding ID. This SubType is encoded as a string. A single
PPAQ MUST NOT contain more than one Rating-Group-ID.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VALUE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(11)
LENGTH : 2 + 4
VALUE : Data type string with a length of 4 octets
Rating-Group-ID SubType
4.3.12. Termination-Action SubType
The value of the type field of the Termination-Action SubType is TBD.
The length of this SubType is 3 octets. This SubType contains an
enumeration of the action to take when the PPS does not grant
additional quota. Valid actions are as follows.
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0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | Action |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(12)
LENGTH : 2 + 1
Action : Data type string.
The content is a byte (with the values 0 to +255).
Termination-Action SubType
The following values for the Termination-Action SubType are defined:
Value | Description
-------------+------------------------------------
0 | Reserved
1 | Terminate
2 | Request More Quota
3 | Redirect/Filter
4..255 | **Available for IANA registration**
Figure 13: Values for the Termination-Action SubType
4.3.13. Pool-ID SubType
The Pool-ID SubType identifies the resource pool. It is encoded as a
string.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | Poolid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(13)
LENGTH : 2 + 4
Poolid : Data type string with length of 4 octets.
Pool-ID SubType
4.3.14. Pool-Multiplier SubType
The Pool-Multiplier SubType determines the weight of resources when
they are inserted into the pool that is identified by the
accompanying Pool-ID SubType, and the rate at which resources are
taken out of the pool by the relevant Service or Rating-Group.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(14)
LENGTH : 2 + (8 or 12)
VALUE : Data type String
The content of the VALUE field either contains the
Value-Digits Field (8 octets long) or the Value-Digits Field
plus the Exponent Field (12 octets long).
Pool-Multiplier SubType
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4.3.15. Requested-Action SubType
The Requested-Action SubType is only be present in messages sent from
the PPC to the PPS. It indicates that the PPC desires the PPS to
perform the indicated action and to return the result. The PPAQ in
which a Requested-Action SubType occurs MUST NOT contain a QID, and
MUST contain a Service-Identifier or a Rating-Group-Identifer that
allows the PPS to uniquely identify the service for which the
indicated action is requested.
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | Action |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(15)
LENGTH : 2 + 1
Action : Data type string.
The content is a byte (with the values 0 to +255).
The values are listed below.
Requested-Action SubType
The following values for the Action field of the Requested-Action
SubType are defined:
Value | Description
-------------+-------------------------------------
0 | Reserved
1 | Balance Check
2 | Price Enquiry
3..255 | **Available for IANA registration**
Figure 14: Values for the Requested-Action SubType
4.3.16. Check-Balance-Result SubType
The Check-Balance-Result SubType can only be present in messages sent
from the PPS to the PPC. It indicates the balance check decision of
the PPS about a previously received Balance Check Request (as
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indicated in a Requested-Action SubType). The PPAQ attribute in
which a Check-Balance-Result occurs MUST NOT include a QID beause no
quota is reserved by the PPS.
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | Decision |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(16)
LENGTH : 2 + 1
Decision : Data type string.
The content is a byte (with the values 0 to +255).
The values are listed below.
Check-Balance-Result SubType
The following values for the Decision field of the Check-Balance-
Result SubType are defined:
Value | Description
-------------+-------------------------------------------
0 | Success; Sufficient funds available
| in the user's prepaid account
1 | Failure; Insufficient funds available
2..255 | **Available for IANA registration**
Figure 15: Values for the Check-Balance-Result SubType
4.3.17. Cost-Information SubType
The Cost-Information SubType is used in order to return the cost
information of a service, which the PPC can transfer transparently to
the end user. This SubType is sent from the PPS to the PPC as a
response to a "Price Enquiry", as indicated by the Requested-Action
SubType.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(17)
LENGTH : 2 + 12 + 4 + length of the Cost-Unit Field
VALUE : Data type String
The content of the VALUE field contains (in this order) the
Value-Digits Field, Exponent Field, Currency-Code Field
and the Cost-Unit Field.
Cost-Information SubType
For example, the cost of 7.75 Malawi kwacha per hour would be encoded
as follows. Value-Digits = 775, Exponent = -2, Currency Code = 454,
and Cost-Unit = "hour".
The PPAQ that carries a Cost-Information MUST NOT include a QID.
The Currency-Code Field is of type Unsigned32 and used inside the
Check-Balance-Result SubType and contains a currency code that
specifies in which currency the values of AVPs containing monetary
units were given. It is specified by using the numeric values
defined in the ISO 3166-1 standard.
The Cost-Unit Field is used inside the Check-Balance-Result SubType
and contains a human readable UTF8 encoded string that can be
displayed to the end user. It specifies the applicable unit to the
Cost-Information when the service cost is a cost per unit (e.g., cost
of the service is $1 per minute). The Cost-Unit can, for example, be
minutes, hours, days, kilobytes, megabytes, etc.
4.4. Fields
4.4.1. Value-Digits Field
The Value-Digits Field is an Unsigned64 value (with a length of 8
octets) that contains the significant digits of the number. If
decimal values are needed to present the number, the scaling MUST be
indicated with a related Exponent Field, see Section 4.4.2.
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For example, the decimal number 0.05 is encoded by a Value-Digits
Field set to 5, and a scaling that is indicated with the Exponent
Field set to -2.
The encoding of this SubType is not done in an TLV format but rather
the encoded value is added to existing subtypes.
4.4.2. Exponent Field
The Exponent field is a Integer32 value that contains the exponent
value that is to be applied to the accompanying Value-Digit Field.
4.5. Prepaid Tariff Switching (PTS) Attribute
This specification defines the PTS attribute, which allows to switch
from one rate to another during service provision. Support for
tariff switching is optional to implement and to use for the PPC and
the PPS. PPCs use the flag "Tariff Switching supported" in the
AvailableInClient field of the PPAC attribute in order to indicate
support for tariff switching. PPSs employ the PTS attribute in order
to announce their support for tariff switching.
If a RADIUS message contains a PTS attribute, it MUST also contain at
least one PPAQ attribute. If a RADIUS Access-Request message
contains a PTS attribute or the "Tariff Switching supported" flag in
the AvailableInClient field of the PPAC attribute, it MUST also
contain an Event-Timestamp RADIUS attribute (see [RFC2869]).
Every PTS attribute MUST include a QID SubType, as specified in
Section 4.3.1. In a RADIUS Access-Request message sent from the PPC
to the PPS, the QID SubType MUST contain the value of the Quota
Identifier SubType that was previously received from the PPS and MUST
be the same as the value carried in the QID SubType of one of the
PPAQ attributes included the same RADIUS message.
If multiple services are supported and if the PPAQ is associated with
a service as indicated by the Service-ID SubType, then the PTS refers
to the tariff switch for that service. If the PPAQ does not have a
Service-ID, then the PTS refers to tariff switch for the "Access
Service".
A PPAQ attribute that is transported along with a PTS attribute and
has the same value as the QID SubType contained in the PTS attribute
in its own QID SubType is referred to as the "accompanying PPAQ
attribute". If a PPS receives an Access-Request message from a PPC,
it associates a unique value for the QID SubType to this request.
The following table summarizes the presence of various SubTypes in
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the PTS attribute carried in the Access-Request and Access-Accept
messages.
Request Accept # SubType Name
1 1 1 Quota Identifier
1 0 2 VolumeUsedAfterTariffSwitch
0 0-1 3 TarrifSwitchInterval
0 0-1(a) 4 TimeIntervalAfterTarriffSwitchUpdate
None of the above-listed SubTypes appears in the Access-Reject nor in
the Access-Challenge.
Notes:
(a) The PPS SHALL include this AVP if there is another tariff
switch period after the period that ends as indicated by the TSI
attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Vendor-Id
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Vendor-Id (cont) | Vendor type | Vendor length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Continuation | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
The fields have the following meaning and encoding:
Type:
26 for Vendor-Specific
Length:
6 + 3 + length of SubTypes
Vendor-Id:
The Vendor-Id value for WiMAX is 24757.
Vendor type:
38 for PTS
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Vendor length:
3 + length of SubTypes
Continuation:
The Continuation Field is defined as follows:
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|C|r|r|r|r|r|r|r|
+-+-+-+-+-+-+-+-+
The C-bit of the continuation field indicates
if a attribute is being fragmented. When the
C-bit is set to one '1' this indicates that
the attribute is being fragmented that is
the next VSA of the same type is to be appended
to this attribute. When the C-bit is set to zero
'0' this indicates that the next attribute is
not a fragment of this attribute.
An attribute that is not being fragmented will
have the C-bit set to '0'. An attribute that is
being fragmented will have its C-bit set to '1'
for all fragments until the last fragment, which
will have its C-bit set to '0' indicating it's
the last fragment of the attribute. The r-bits
are reserved for future use. They SHALL be set
to zero by the sender and SHALL be ignored by
the receiver.
The value of the C-bit MAY be 0 or 1.
VALUE : Variable length content of data type String containing
one or multiple SubTypes.
Each SubType is then encoding in the following style:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType:
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Contains an 8 bit unsigned integer.
LENGTH:
Contains an 8 bit unsigned integer.
VALUE:
Contains the content of the SubType.
Figure 16: PTS Attribute
4.5.1. VolumeUsedAfterTariffSwitch SubType
The optional VolumeUsedAfterTariffSwitch (VUATS) SubType is used in
the RADIUS Access-Request messages (PPC to PPS direction). It
indicates the volume (in octets) used during a session after the last
tariff switch for the service specified via the QID SubType and the
accompanying PPAQ attribute.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(23)
LENGTH : variable (8 or 14)
VALUE : Data type String
The content of the VALUE field either contains the
Value-Digits Field or the Value-Digits Field plus the
Exponent Field. The length field indicates whether one or
both subtypes are included.
VolumeUsedAfterTariffSwitch SubType
4.5.2. TariffSwitchInterval SubType
The TariffSwitchInterval (TSI) SubType MUST be present in each PTS
attribute that is part of a RADIUS Access-Accept message (PPS to PPC
direction). It indicates the interval (in seconds) between the value
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of Event-Timestamp RADIUS attribute (see [RFC2869]) of the
corresponding RADIUS Access-Request message and the next tariff
switch condition.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VALUE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(24)
LENGTH : 6
VALUE : Data type string
This field contains a 16-bit unsigned integer
(with the values 0 to +65,535).
TariffSwitchInterval SubType
4.5.3. TimeIntervalafterTariffSwitchUpdate SubType
The PPS MUST include TimeIntervalafterTariffSwitchUpdate (TITSU)
SubType if there is another tariff switch period after the period
that ends as indicated by the TSI SubType. The value of the TITSU
SubType contains the number of seconds of the tariff period that
begins immediately after the period that ends as indicated by the TSI
attribute. If the TITSU SubType is not present, the PPC assumes that
the tariff period, which ends as indicated by the TSI SubType, lasts
until further notice. If TITSU is specified, the PPC MUST send a
quota update before the point in time specified by the TITSU SubType
(see Figure 7).
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | LENGTH | VALUE ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VALUE |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields have the following meaning and encoding:
SubType : Value(25)
LENGTH : 6
VALUE : Data type string
This field contains a 16-bit unsigned integer
(with the values 0 to +65,535).
TimeIntervalafterTariffSwitchUpdate SubType
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5. Diameter RADIUS Interoperability
The RADIUS Prepaid extension described in this document may need to
interoperate with the Diameter Credit Control Application. Two
interoperability scenarios exist, as follows. Either the AAA server
is Diameter based and the AAA client is RADIUS based, or the AAA
client is Diameter based and the AAA server is RADIUS based.
The Diameter Credit Control Application [RFC4006] describes how to
implement a prepaid accounting system using a Diameter based
infrastructure.
A possible procedure for accomplishing the translation of the
functionality defined in Diameter Credit Control and in the RADIUS
Prepaid specification is described in Appendix B.
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6. Security Considerations
This specification describes the use of RADIUS for purposes of real-
time accounting. Threats and security issues for this application
are described in [RFC3579] and [RFC3580]; security issues encountered
in roaming are described in [RFC2607].
This document specifies new attributes that can be included in
existing RADIUS packets, which are protected as described in
[RFC3579] and [RFC3576]. See those documents for a more detailed
description.
The security mechanisms supported in RADIUS are focused on preventing
an attacker from spoofing packets or modifying packets in transit.
They do not prevent an authorized RADIUS/Diameter server or proxy
from modifying, inserting, or removing attributes with malicious
intent. When the attributes defined in this document are modified or
removed by a RADIUS proxy they may lead to incorrect accounting
records being delivered to users or wrong resource consumption being
collected.
The described mechanism add the mechanism of capability negotiation,
so that a RADIUS server can automatically discover whether a NAS
supports the real-time accounting features described in this document
(and even more detailed capabilities can be learned by the RADIUS
server). These mechanisms are being added to ensure that neither the
NAS nor the RADIUS server make incorrect assumptions about the
capabilities of the other party; potentially leading to incorrect
accounting and improper access to the network or other services.
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7. Table of Attributes
The following table provides a guide which attributes may be found in
which RADIUS messages, and in what quantity.
Request Accept Reject Challenge Accounting # Attribute
Request
0-1 0 0 0 0 35 PPAC
0-1 0 0 0 0 36 Session Termination
Capability
0+ 0+ 0 0 0+ 37 PPAQ
0+ 0+ 0 0 0+ 38 PTS
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8. IANA Considerations
This document contains a number of instructions to IANA.
8.1. RADIUS Attributes
This document does not require IANA to register the following four
RADIUS attributes as the code registered by the Wimax Forum is re-
used. The Wimax Forum SMI Network Management Private Enterprise Code
is 24757.
Attribute Name | Attribute Type Value
--------------------------------------+-----------------------------
Prepaid-Accounting-Capability (PPAC) | 35
Session Termination Capability | 36
Prepaid-Accounting-Operation (PPAQ) | 37
Prepaid Tariff Switching (PTS) | 38
8.2. New Registry: PPAC SubTypes
Section 4.1 defines the SubTypes used within the PPAC attribute.
IANA is asked to create a registry for these SubTypes. Each registry
entry consists of a 8 bit number together with a description of the
PPAC SubType. This document creates the following PPAC SubTypes for
this registry:
Value | SubType Name
---------+-----------------------------
0 | Reserved
1 | AvailableInClient
2..255 | **Available for IANA registration**
The semantic of the above-listed SubType is described in Section 4.1.
Following the policies outline in [RFC3575] the available SubTypes
(i.e., value 0 and values 2-255) with a description of their semantic
will be assigned after the expert review process. Updates can be
provided based on expert approval only. Based on expert approval it
is possible to mark entries as "deprecated". A designated expert
will be appointed by the IESG.
Each registration must include a number for the SubType and the
semantic of the SubType.
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8.3. New Registry: PPAQ SubTypes
Section 4.3 defines the SubTypes used within the PPAQ attribute.
IANA is asked to create a registry for these SubTypes. Each registry
entry consists of a 8 bit number together with a description of the
PPAQ SubType. This document creates the following PPAQ SubTypes for
this registry:
Value | SubType Name
---------+-----------------------------
0 | Reserved
1 | Quota Identifier
2 | VolumeQuota
3 | VolumeThreshold
4 | DurationQuota
5 | DurationThreshold
6 | ResourceQuota
7 | ResourceThreshold
8 | Update-Reason
9 | PrepaidServer
10 | Service-ID
11 | Rating-Group-ID
12 | Termination-Action
13 | Pool-ID
14 | Pool-Multiplier
15 | Requested-Action
16 | Check-Balance-Result
17..255 | **Available for IANA registration**
The semantic of the above-listed SubTypes is described in
Section 4.3.
Following the policies outline in [RFC3575] the available SubTypes
(i.e., value 0 and values 22-255) with a description of their
semantic will be assigned after the expert review process. Updates
can be provided based on expert approval only. Based on expert
approval it is possible to mark entries as "deprecated". A
designated expert will be appointed by the IESG.
Each registration must include a number for the SubType and the
semantic of the SubType.
8.4. New Registry: PTS SubTypes
Section 4.5 defines the SubTypes used within the PTS attribute. IANA
is asked to create a registry for these SubTypes. Each registry
entry consists of a 8 bit number together with a description of the
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PTS SubType. This document creates the following PTS SubTypes for
this registry:
Value | SubType Name
---------+-----------------------------
0 | Reserved
1 | Quota Identifier
2 | VolumeUsedAfterTariffSwitch
3 | TariffSwitchInterval
4 | TimeIntervalafterTariffSwitchUpdate
5..255 | **Available for IANA registration**
The semantic of the above-listed SubTypes is described in
Section 4.5.
Following the policies outline in [RFC3575] the available SubTypes
(i.e., value 0 and values 5-255) with a description of their semantic
will be assigned after the expert review process. Updates can be
provided based on expert approval only. Based on expert approval it
is possible to mark entries as "deprecated". A designated expert
will be appointed by the IESG.
Each registration must include a number for the SubType and the
semantic of the SubType.
8.5. New Registry: Update-Reason
Section 4.3.8 defines the Update-Reason SubType. IANA is asked to
create a registry for the values contained in the Update-Reason
SubType, as shown in Figure 12. Each registry entry consists of a 16
bit number together with a description of the update reason.
Following the policies outline in [RFC3575] the available values
together with a description of their semantic will be assigned after
the expert review process. Updates can be provided based on expert
approval only. Based on expert approval it is possible to mark
entries as "deprecated". A designated expert will be appointed by
the IESG.
8.6. New Registry: Termination-Action
Section 4.3.12 defines the Termination-Action SubType. IANA is asked
to create a registry for the values contained in the Termination-
Action SubType, as shown in Figure 13. Each registry entry consists
of a 8 bit number together with a description of the termination
action.
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Following the policies outline in [RFC3575] the available values
together with a description of their semantic will be assigned after
the expert review process. Updates can be provided based on expert
approval only. Based on expert approval it is possible to mark
entries as "deprecated". A designated expert will be appointed by
the IESG.
8.7. New Registry: Requested-Action
Section 4.3.15 defines the Requested-Action SubType. IANA is asked
to create a registry for the values contained in the Requested-Action
SubType, as shown in Figure 14. Each registry entry consists of a 8
bit number together with a description of the requested reason.
Following the policies outline in [RFC3575] the available values
together with a description of their semantic will be assigned after
the expert review process. Updates can be provided based on expert
approval only. Based on expert approval it is possible to mark
entries as "deprecated". A designated expert will be appointed by
the IESG.
8.8. New Registry: Check-Balance-Result
Section 4.3.16 defines the Check-Balance-Result SubType. IANA is
asked to create a registry for the values contained in the Check-
Balance-Result SubType, as shown in Figure 15. Each registry entry
consists of a 8 bit number together with a description of the
requested reason.
Following the policies outline in [RFC3575] the available values
together with a description of their semantic will be assigned after
the expert review process. Updates can be provided based on expert
approval only. Based on expert approval it is possible to mark
entries as "deprecated". A designated expert will be appointed by
the IESG.
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9. Acknowledgements
The authors would like to thank Bernard Aboba, Christian Guenther,
Dirk Kroeselberg and John Loughney for their feedback throughout the
development of this document. Additionally, the authors would like
to thank the members of the Wimax Forum and the members of 3GPP2 for
their help with this specification.
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10. References
10.1. Normative References
[RFC2119] Bradner, S., "RFC 2119: Key words for use in RFCs to
Indicate Requirement Levels", March 1997.
[RFC2865] Rigney, C., Rubens, A., Simpson, W., and S. Willens, "RFC
2865: Remote Authentication Dial In User Server (RADIUS)",
June 2000.
[RFC3576] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
Adoba, "RFC 3576: Dynamic Authorization Extensions to
Remote Authentication Dial-In User Service (RADIUS)",
February 2003.
10.2. Informative References
[RFC2284] Blunk, L. and J. Vollbrecht, "PPP Extensible
Authentication Protocol (EAP)", RFC 2284, March 1998.
[RFC2607] Aboba, B. and J. Vollbrecht, "Proxy Chaining and Policy
Implementation in Roaming", RFC 2607, June 1999.
[RFC2866] Rigney, C., "RFC 2866: RADIUS Accounting", June 2000.
[RFC2869] Rigney, C., Willats, W., and P. Calhoun, "RFC 2869: RADIUS
Extensions", June 2000.
[RFC3575] Aboba, B., "IANA Considerations for RADIUS (Remote
Authentication Dial In User Service)", RFC 3575,
July 2003.
[RFC3579] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication
Dial In User Service) Support For Extensible
Authentication Protocol (EAP)", RFC 3579, September 2003.
[RFC3580] Congdon, P., Aboba, B., Smith, A., Zorn, G., and J. Roese,
"IEEE 802.1X Remote Authentication Dial In User Service
(RADIUS) Usage Guidelines", RFC 3580, September 2003.
[RFC3748] Adoba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "RFC 3748: Extensible Authentication Protocol",
June 2004.
[RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
Loughney, "RFC 4006: Diameter Credit Control Application",
August 2005.
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[RFC4849] Congdon, P., Sanchez, M., and B. Aboba, "RADIUS Filter
Rule Attribute", RFC 4849, April 2007.
[RFC6158] DeKok, A. and G. Weber, "RADIUS Design Guidelines",
BCP 158, RFC 6158, March 2011.
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Appendix A. Example flows
Note: This section is informative.
This section presents certain example flows that involve the RADIUS
prepaid extensions. By no means is the intent of this section to
specify or recommend business logic, rating strategies, and
application-level behaviour. The intent of this section is purely to
illustrate some fictive scenarios and the RADIUS prepaid message
flows that could be associated with these scenarios. The contents of
this section should be regarded as a collection of informative
examples that aim to provide guidance to implementors.
A.1. A simple flow
End user PPC PPS
user logs on
------(1)--------->
Access Request
{RADIUS BASE AVPS,
PPAC=00...00011}
-------(2)-------->
[allocates
5MB quota]
Access Accept
{RADIUS BASE AVPS,
PPAQ={QID=5, VQ = 5MB,
VTH = 4.5 MB}}
<-------(3)--------
service provision/metering
-------(4)--------->
4.5 MB consumed
Access Request
{RADIUS BASE AVPS,
PPAQ={QID=5, VQ=4.5MB,
REASON=THRESHOLD REACHED}}
-------(5)--------->
[allocates another 7MB
to the access service]
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Access Accept
{RADIUS BASE AVPS,
PPAQ={QID=8, VQ=12MB,
VTH = 11.5 MB}}
<----------(6)--------------
user logs off
------(7)-------
Access Request
{RADIUS BASE AVPS,
PPAQ={QID=8, VQ=7 MB,
REASON=ACCESS SERV TERMINATED}}
-------(8)--------->
[reimburses
user account]
AA Accept
{RADIUS BASE AVPS}
<-------(9)--------
Figure 17: A simple example message flow
The user logs on (1). The PPC sends a RADIUS Access Request message
to the PPS (2), and includes the prepaid-specific PPAC AVP. This AVP
indicates that both duration-based and volume-based metering is
supported. However, it also indicated that multiple services, rating
groups and resource pools are not supported. Note that, since this
is not an "Authorize-Only" message, no PPAQ attribute with Update
Reason="initial request" is included (see Section 3.7.1). The PPS
then authenticates the user and authorizes the access service, as is
usual in RADIUS. Note that the PPAC AVP is appended by the PPC in at
least the last message that is sent to the home AAA server during
this possibly multiple-round exchange.
If authentication and authorization is successful (in this example
this is assumed), then the PPS identifies the user's prepaid account
from the included base RADIUS AVPs, and determines the capabilities
of the PPC from the PPAC attribute. Assuming that sufficient funds
are available in the user's prepaid account, the PPS reserves some of
these and rates the service. In this example, the PPS reserves, say,
2 Euros and determines that the access service is rated at 0.4 Euro
per MB. This results in 5 MB of quota being granted. The PPS also
determines that the PPC should ask for this quota to be replenished
once 4.5 MB have been consumed. Thus, it creates an Access Accept
message with a Volume-Threshold indication of 4.5MB. It further
associates the QID=5 to this reservation. This identifier can be
used to later uniquely identify the prepaid session, user, account,
etc. The resulting Access Accept message is sent to the PPC (3).
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Upon reception of message (4), the PPC provides the access service to
the user and meters it accordingly. At some point in time, the
threshold is reached, i.e., 4.5MB of "access service" have been
consumed by the user. At that point, the PPC generates an Authorize-
Only Access Request that contains the usual RADIUS attributes and a
PPAQ attributes that reports the amount of consumed quota, and the
request for replenishment, i.e., the Update-Reason= THRESHOLD REACHED
(5). Note that the QID in this message is the same as the one
previously received from the PPS.
Upon reception of message (5), the PPS identifies the user and his
account from the QID. In also determines that a prepaid session is
ongoing, and that enough credit remains in the prepaid account in
order for the access service to continue being provided. Since 4.5
MB have been consumed, the PPS subtracts 1.8 Euros from the user's
prepaid account. The PPS decides to reserve another 2.8 euros from
the user's account. (This results in 3 euros being reserved in total
at this point in time.) As the access service is rated at 0.4 euros
per MB, the PPS determines that another 7 MB of quota should be
granted. This results in a total cumulative quota allocation of 12
MB for the access service. The PPS further calculates the new
threshold value of 11.5 MB. Since this is a new quota reservation,
the PPS also allocates a new QID to it, in this example QID=8. The
resulting RADIUS message is sent to the PPC (6).
Upon reception of message (6), the PPC updates its records and
continues provisioning access to the user. At some point the user
logs off (7). The PPC must then report how many resources were
consumed, so that the PPC can subtract the appropriate monetary
amount from the user's prepaid account. To this end the PPC
constructs an Authorize-Only Access Request message with a PPAQ
attributes for the access service. In this example, 7 MB were
consumed by the access service in total. The PPC reports 7 MB its
final message (8). The PPS correlates the report, using the QID, to
the previous session state. It determines, from the previous
records, that the access service had consumed another 4.5 MB before
(as indicated in message (6)). This means that, of the 7 MB, only
3.5 MB have not yet been subtracted from the user's account. Thus,
the PPS subtracts another 1.4 euros from the user's account and,
since the session is to be terminated (REASON=ACCESS SERVICE
TERMINATED), releases any reserved monetary amount.
The PPS responds with an Access Response as required by the RADIUS
base specification (9).
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A.2. A flow with prepaid tariff switching
End user PPC PPS
user logs on
------(1)--------->
Access Request
{RADIUS BASE AVPS,
PPAC=00...00111}
-------(2)-------->
[allocates
20MB quota]
Access Accept
{RADIUS BASE AVPS,
PPAQ={QID=5, VQ = 20MB,
VTH = 18 MB}, PTS={
QID=5, PTS{TSI=300sec,
TITSU=6000sec}}
<-------(3)-------
service provision/metering
-------(4)--------->
5900 seconds
passed
Access Request
{RADIUS BASE AVPS,
PPAQ={QID=5, VQ=14MB,
REASON=TITSU APPROACH.},
TSI={QID=5, VUATS=11MB}}
-------(5)--------->
[allocates another 10MB
to the access service]
Access Accept
{RADIUS BASE AVPS,
PPAQ={QID=8, VQ=30MB,
VTH = 28 MB},PTS={
QUD=8, PTS=95 sec}}
<----------(6)--------------
user logs off
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------(7)-------
Access Request
{RADIUS BASE AVPS,
PPAQ={QID=8, VQ=17 MB,
REASON=ACCESS SERV TERMINATED},
PTS={QID=8, VUATS=2.5 MB}
-------(8)--------->
[reimburses
user account]
AA Accept
{RADIUS BASE AVPS}
<-------(9)--------
Figure 18: Example message flow with Tariff Switch
The user logs on (1). The PPC sends a RADIUS Access Request message
to the home AAA server (2), and includes the prepaid-specific PPAC
AVP. This AVP indicates that both duration-based and volume-based
metering is supported, as well as tariff switching. The home AAA
server then may authenticate and user and authorize the access
service, as is usual in RADIUS. Note that the PPAC AVP is appended
by the PPC in at least the last message that is sent to the PPS
during this possibly multiple-round exchange.
If authentication and authorization is successful (in this example
this is assumed), the PPS identifies the user's prepaid account from
the included base RADIUS AVPs, and determines the capabilities of the
PPC from the PPAC attribute. In this example, it is assumed that a
tariff switch is about to occur in 300 seconds from the current time.
Suppose that the access service is currently rated at 0.5 euros per
MB and in the next tariff period it is rated at 0.6 euros per MB.
Suppose further that a third tariff period is about to start in 6000
seconds from current time and that that access service is rated at
0.8 euros per MB in that period. The PPS then decides to reserve 12
euros from the user's account. Since it is conceivable that the user
may consume all allocated quota in the (more expensive) "0.6-euro"
period, the PPS reserves 20 MB of quota, and determines a threshold
value of 18 MB. It constructs a Radius Access Accept message with a
PPAQ attribute that reflects these choices, and carries a Quota
Identifier QID=5. It further adds a PTS AVP in the message which is
linked to the PPAQ via the common QID value. The PTS AVP contains a
TSI attribute indicating that a tariff switch will occur in 300
seconds. It also includes a TITSU attribute with the value of 6000
seconds. This is included in order to make sure that the PPC will
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report the consumed quota before the "2-euro" tariff period will
start. The message is sent to the PPC (3).
Upon reception of message (3), the PPC provides the access service to
the user and meters it accordingly (4). It also keeps track of time.
That is, it remembers how many octets are consumed before and how
many after the tariff switch that will take place in 300 seconds.
In this example it is assumed that the user consumes the allocated
quota rather slowly. In particular, nearly 6000 seconds (the value
indicated by TITSU SubType) pass without the threshold of 18 MB being
reached. The PPC notices this and must therefore report usage and
request the quota to be replenished despite the fact that the
threshold has not been reached. In this example, it decides to do so
100 seconds before the 6000 seconds are reached. To this end, it
constructs an Authorization Access Request message including a PPAQ
that indicates that 14 MB have been consumed up to now. It also
includes a PTS attribute in order to indicate, using the VUATS
SubType, that 11 MB of these were consumed after the tariff switch.
The message is sent to the the PPS (5).
The PPS can link the message to previous session state via the QID.
It now rates the consumed volume as follows. The 11 MB that were
consumed after the tariff switch correspond to 11 * 0.6 = 6.6 euros
and the remaining 14-11=3 MB to 3 * 0.5 = 1.5 euros. Thus, the PPS
subtracts the amount of 6.6+1.5=8.1 euros from the user's account,
which leads to a remainder of 12 - 8.1 = 3.9 euros being reserved.
The PPS now determines that message (5) was sent in order to
replenish the quota for this prepaid session. This can be deduced
from the UPDATE REASON field, which indicates that the PPC sent this
message because the time indicated by the TITSU SubType is
approacing. The PPS now determines that enough credit remains in the
user's prepaid account in order for the access service to continue
being provided and decides to reserve another 8.9 euros from the
user's account. Since it is conceivable that the user will consume
the 6 unused MB of quota from the previous allocation, as well as the
entire quota that is to be allocated now, entirely in the "0.8-euro"
period, the quota that should now be granted in addition to the
previous 20 MB should be 10 MB. This is because 0.9 of the 8.9 euros
are being reserved in order to "cover the worst case scenario". The
fact that 0.9 euros are reserved for this purpose is due to the fact
that the unused 6 MB from the previous allocation correspond to 4.8
euros (with 0.8 euros per MB). This is 4.8 - 3.9 = 0.9 euros more
than the amount of funds that are still "reserved" from the previous
allocation. (After this reservation, the total amount of reserved
money is 8.9 + 3.9 = 12.8 euros, which corresponds to 16 (10+6) MB
being consumed in the "0.8-euro" period.)
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Since quotas are encoded in a cumulative way in RADIUS, the PPS
includes a VolumeQuota of 30 MB into the Access Accept message (6).
The PPS further calculates the new threshold value of 28 MB. Since
this is a new quota reservation, the PPS also allocates a new QID to
it, in this example QID=8. The resulting RADIUS message is sent to
the PPC (6).
Upon reception of message (6), the PPC updates its records and
continues providing access to the user. At some point the user logs
off (7). The PPC must then report how many resources were consumed,
so that the PPC can subtract the appropriate monetary amount from the
user's prepaid account. To this end the PPC constructs an Authorize-
Only Access Request message with a PPAQ attributes for the access
service. In this example, 17 MB were consumed by the access service
in total. The PPC reports 17 MB its final message (8). The PPS
correlates the report, using the QID, to the previous session state.
It determines, from the previous records, that the access service had
consumed 14 MB before (as indicated in message (5)). This means
that, of the 17 MB, only the monetary equivalent for 3 MB have not
yet been subtracted from the user's account. The PPS calculates how
much should be deducted from the user's account as follows. Since
the VUATS SubType indicates that 2.5MB were consumed after the tariff
switch, only 0.5 MB were consumed before that. Thus, the monetary
equivalent is 0.5 * 0.6 + 2.5 * 0.8 = 3.6 euros. That is, the PPS
subtracts 3.6 euros from the user's prepaid account. Since the
session has by now be terminated by the PPC (REASON=ACCESS SERVICE
TERMINATED), the PPS now releases any reserved monetary amount, in
this example 12.8 - 3.6 = 9.2 euros.
The PPS responds with an Access Response as required by the RADIUS
base specification (9).
Remark: In this example, two tariff switches take place. In other
scenarios, of course, only one tariff switch may occur. In such
scenarios the TITSU SubType is not used.
A.3. Resource pools and Rating Groups
End user PPC PPS
user logs on
------(1)--------->
Access Request
{RADIUS BASE AVPS,
PPAC=00...00101111}
-------(2)-------->
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[allocates
5MB quota]
Access Accept
{RADIUS BASE AVPS,
PPAQ={QID=5, VQ = 5MB,
poolID=1,mult=1}}
<-------(3)--------
service provision/metering
-------(4)--------->
user requests service A
-------(5)--------->
Access Request
{RADIUS BASE AVPS,PPAQ={
SID="A", RGROUP=1}}
-------(6)-------->
[allocates 50 min
quota]
Access Accept
{RADIUS BASE AVPS,
PPAQ={QID=7, DQ=3000sec
poolID=1,RGROUP=1, SID="A"
mult=1747.63}}
<---------(7)---------------
user requests service B
-------(8)-------->
Pool 1 close to exhaustion
Access Request
{RADIUS BASE AVPS,
PPAQ={QID=5, VQ=4MB,
REASON=QUOTA REACHED,
PoolID=1, mult=1}
PPAQ={QID=7, DQ=3300sec
REASON=QUOTA REACHED,
PoolID=1, mult=1747.63,
SID="A",RGROUP=1}}
-------(9)--------->
[allocates another
3 MB to access service
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and 30 minutes to
service "A"]
Access Accept
{RADIUS BASE AVPS,
PPAQ={QID=8, VQ=8MB,
PoolID=1, mult=1, RGROUP=1},
PPAQ={QID=9, DQ=4800sec
PoolID=1, mult=1747.63,
SID="A"}}
\ <----------(10)--------------
user logs off
------(11)-------
Access Request
{RADIUS BASE AVPS,
PPAQ={QID=8, VQ=6.5MB,
REASON=ACCESS SERV TERMINATED,
PoolID=1, mult=1}
PPAQ={QID=9, DQ=5400sec
REASON=ACCESS SERV TERMINATED,
PoolID=1, mult=1747.63,
SID="A",RGROUP=1}}
-------(12)--------->
[reimburses
user account]
AA Accept
{RADIUS BASE AVPS
<------(13)--------
Figure 19: Example message flow with resource pools and rating groups
The user logs on (1). The PPC sends a RADIUS Access Request message
to the PPS (2), and includes the prepaid-specific PPAC AVP,
indicating that multiple services, rating groups and resource pools
are supported. Note that, since this is not an "Authorize- Only"
message, no PPAQ attribute with Update Reason="initial request" is
included (see Section 3.7.1). The PPS then may authenticate the user
and authorize the access service, as is usual in RADIUS. Note that
the PPAC AVP is appended by the PPC in at least the last message that
is sent to the PPS during this possibly multiple-round exchange.
If authentication and authorization is successful (in this example
this is assumed), the PPS identifies the user's prepaid account from
the included base RADIUS AVPs, and determines the capabilities of the
PPC from the PPAC attribute. Assuming that sufficient funds are
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available in the user's prepaid account, the PPS reserves some of
these and rates the service. In this example, the PPS reserves 5
Euros and determines that the access service is rated at 1 Euro per
MB. In anticipation that the user requests more chargeable services
throughout this prepaid session, and since this is supported by the
PPC, the PPS further associates a resource pool with this
reservation, in this example PoolID=1. The PPC also specifies the
multiplier = 1 for the access service. Note that, since 5MB =
5242880 octets, 1 unit in the resource pool corresponds to 5 /
5242880 euros, which is about 0.000095367431640625 Eurocents.
(However, the PPC does not need to know that.) Moreover, the PPS
associates the QID=5 to this reservation. This identifier can be
used to later uniquely identify the prepaid session, user, account,
etc. The resulting Access Accept message is sent to PPC (3).
Upon reception of message (3), the PPC provides the access service to
the user and meters it accordingly (4). That is, for every octet
consumed, the PPC subtracts 1 unit (since the multiplier is 1) from
the resouce pool with PoolID=1.
At some point in time, the user requests another chargeable service,
namely service A (5). The PPC generates an Authorize-Only Access
Request that contains the usual RADIUS attributes and the Service-ID
identifying service A (6). The PPC has determined that service A is
rated in an identical way as at least one more service. Thus,
service A has been configured to belong to a rating group, in this
example the group with Rating-Group-ID=1. This identifier is
included is message (6).
Upon reception of message (6), the PPS identifies the user and his
account from the base RADIUS attributes, the fact that a prepaid
session is ongoing, and determines that enough credit remains in the
prepaid account in order for service A to be provided. The PPS also
determines that service A is rated at 0.10 euros per minute. The PPS
decides to reserve another 5 euros from the users account; this
corresponds to 50 minutes or, as encoded in the DurationQuota
SubType, 3000 seconds. As service A draws from the same prepaid
account as the access service, the PPS associates this reservation
with the same resource pool as the previous reservation (QID=5),
namely the pool with PoolID=1. Note that, in order for the abstract
units in the pool to be consistent, the multiplier has to be 1747.63.
This is because each second corresponds to about 0.10 / 60 = 0.00167
euros, which is about 1747.63 times the value of an abstract resource
pool unit, as this was determined by the first allocation of quota to
the pool (i.e., 0.000095367431640625 Eurocents). Since this is a new
quota reservation, the PPS also allocates a new QID to it, in this
example QID=7. The resulting RADIUS message is sent to the PPC (7).
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Upon reception of message (7), the PPC adjusts the units in resource
pool 1. That is, it first determines how much quota had been
allocated to service A in the past, and subtracts this from the quota
reservation found in the message. Since this is the first quota
reservation for service A, there is nothing to subtract. Thus, it
adds 3000 * 1747.63 = 5242890 units to the pool and remembers that
3000 seconds have been allocated to service A during this prepaid
session. The PPC then provides service A to the user, and meters it
against resource pool 1. That is, for every second it subtracts
1747.63 units from the pool.
At some point in time, the user requests service B (8). The PPC
determines that service B is rated exactly in the same way as service
A, i.e., that they belong to the same rating group, namely the one
with Rating-Group-ID=1. Since this rating group has been effectively
authorised by the allocation of quota with QID=7, the PPC provides
service B to the user immediately. It is rated in the same way as
service A, i.e., for every second provided, 1747.63 units are
subtracted from credit pool 1.
At some point in time, resource pool 1 is close to exhaustion. (For
example, the PPC may determine that the pool is "close to exhaustion"
when has less than 10% its initial amount of units.) At that point,
the PPC needs to ask for replenishment for the pool. Suppose that,
at that point in time, 4MB of "access service", 45 minutes of
"service A", and 10 minutes of "service B" were provided to the user.
Note that this corresponds to (4*1048576) + (55*60*1747.63) = 4194304
+ 5767179 = 9961483 abstract service units from the pool. The PPC
constructs an Authorize-Only Access Request message that reports the
usage for the "access service" and "service A". This message
contains two PPAQ attributeS, is sent to the PPS (9). Note that is
the message it appears that "service A" has consumed more than it was
allocated (i.e., 55 minutes although only 50 minutes were initially
allocated to it). This is not a a problem since the PPS knows that
"service A" was drawing from the same pool as the "access service"
and that the "access service" did only consume 4 out of the 5 MB it
was allocated.
Upon reception of message (9), the PPS subtracts 4 euros from the
user's account for the "access service" and another 5.5 euros for
"service A". (This includes the charge incurred by "service B" up to
that point in time, although the PPS is not aware of "service B"
being provisioned to the user.) The PPS then determines that
sufficient funds remain in the prepaid account in order for both
services to be continued. The PPS decides to reserve another 3MB for
the access service and 30 minutes for "service A". This corresponds
to 3+3=6 euros. Since in RADIUS prepaid the quotas are encoded in a
cumulative manner, the PPAQ attribute that grants the quota for the
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"access service" contains a Volume-Quota SubType of 8MB (8388608
octets), which is the 5MB that were initially allocated, plus the 3MB
allocated now. The resource pool identifier is, as previously,
PoolID=1 and the multiplier is 1. Similarly, the PPAQ that grants
quota for "service A" contains 4800 seconds (the initial 3000 plus
1800 that correspond to the 30 additional minutes). Again, the
PoolID=1 and multiplier=1747.63. The resulting Access Response
message is sent to the PPC (10).
When the PPC received message (10) it checks how much quota has been
allocated previously to the "access service". It finds that the
answer is 5MB (5242880 octets); thus, out of the 8MB (8388608 octets)
that are indicated by the PPAQ with QID=8, only 3MB (3145728 octets)
have not yet been added to resource pool 1. The PPC thus adds
3145728 abstract units to resource pool 1 (since the multiplier is
1). The PPC then acts similarly on the other PPAQ attribute that
exists in message (11). That is, the PPC determines that 3000
seconds of quota for "service A" had already been added to the pool.
Thus only 1800 out of the 4800 should be additionally added to the
pool. Since the applicable multiplier here is 1747.63, the PPC adds
further 3145734 abstract units to the pool 1.
The PPC then continues to provide the access service, "service A" and
"service B" to the user, and meters them against the pool, as
previously.
At some point the user logs off (11). The PPC must then report how
many resources were consumed, so that the PPC can subtract the
appropriate monetary amount from the user's prepaid account. To this
end the PPC constructs an Authorize-Only Access Request message with
two PPAQ attributes; one for the access service and one for "service
A". Suppose that, in total, 6.5MB were consumed by the access
service, 70 minutes were consumed by "service A" and 20 minutes by
"service B". The PPC reports 6.5MB (6815744 octets) and 90 minutes
(5400 seconds) in its final message (12). The PPS determines, from
the previous records, that the access service consumed another 2.5MB
(since 4MB out of the 6.5MB were already reported in message (9), and
that "service A" consumed further 600 seconds. This corresponds to
2.5 + (600/60)*0.1 = 2.5+ 1=3.5 euros. Thus, the PPS only subtracts
2.5 out of the 6 previously reserved euros from the user's prepaid
account and responds with an Access Response as required by the
RADIUS base specification (13).
A.4. One-time charging
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End user PPC PPS
user requests ring tone
------(1)--------->
Access Request
{RADIUS BASE AVPS,
PPAQ={QID=321, SID=X, RQ=650,
REASON=10 (ONE-TIME CHARGING}}
-------(2)--------->
[rates 650 abstract units
deducts from user's account]
Access Accept
{RADIUS BASE AVPS}
<----------(3)--------------
ring tone is delivered
<------(4)-------
Figure 20: Example message flow with one-time charging
The user requests a chargeable ring tone (1). The PPC sends a RADIUS
Access Request message to the PPS (2), and includes a PPAQ attribute
with Update Reason="one-time charging" is included (see
Section 3.8.6). The Service ID indicates to the PPS that the
charging event is connected to a ring tone, so that the PPS can rate
the event accordingly. The PPAQ also contains a unique Quota
Identifier.
The PPS then may authenticate the user as is usual in RADIUS. If
authentication is successful (in this example this is assumed), the
home AAA server forwards the PPC converts the 650 reported abstract
units into monetary value, according to the service type, and debit
the user's account accordingly. This happens, of course, only if
sufficient funds are available in the user's prepaid account. The
PPC then responds with an an Access Accept message (3). The PPS adds
a "session timeout = 0 AVP" (see Section 3.8.6).
A.5. Price enquiry
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End user PPC PPS
user requests AoC
------(1)--------->
Access Request
{RADIUS BASE AVPS,
PPAQ={SID=X, VQ=10MB,
REQ_ACT=2(PRICE ENQUIRY}}
-------(2)--------->
[rates 10MB for requested
service]
Access Accept
{RADIUS BASE AVPS,
PPAQ={SID=X, VQ=10MB,
COST INFORMATION= 0.6 euros
per MB}}
<----------(3)--------------
AoC is delivered
<------(4)-------
Figure 21: Example message flow with price enquiry (advice of charge)
Please refer to Section 2.7.3 for an explanation of this message
flow.
A.6. Balance check
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End User PPC PPS
Access Request
{RADIUS BASE AVPS,
PPAQ={SID=X, VQ=10MB,
REQ_ACT=BALANCE CHECK}}
-------(2)--------->
[rates requested
Service and checks
remaining funds]
Access Accept
{RADIUS BASE AVPS,
PPAQ={SID=X, VQ=10MB,
BALANCE_CHECK_RESULT}}
<----------(3)--------------
Figure 22: Example message flow with balance check
Please refer to Section 2.7.4 for an explanation of this message
flow.
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Appendix B. Translation between RADIUS Prepaid and Diameter Credit
Control
Note: This section is informative.
In scenarios where the service metering device uses the "RADIUS
prepaid" (RPP) protocol for accounting and prepaid charging while the
AAA infrastructure uses the "Diameter Credit Control" (DCC) protocol,
a translation agent that enables the interoperation of both systems,
is desirable. This also applies vice versa, i.e., in scenarios where
the AAA infrastructure uses RADIUS and the service metering device
uses Diameter.
The idea of such a translation agent would be to convert incoming RPP
(resp. DCC) messages into outgoing DCC (resp. RPP) messages. It
would be, in principle, desirable for the translation agent to be
stateless. That is, the agent should not be required to internally
maintain information about each ongoing RADIUS or Diameter session.
However, under the current specification of RPP and DCC, this appears
to be impossible due to a number of reasons. These include the
following.
1. The transport mechanism for DCC is TCP, which requires per-
session state to be maintained at both endpoints of the
communication. Note, however, that, in principle, each DCC
message could be sent over a dedicated TCP connection which is
torn down as soon as the message is sent. This, however, is
likely to be unacceptable in terms of efficiency.
2. While RPP messages encode the cumulative amount of consumed/
requested resources, DCC messages carry the difference from the
previous message. This means that the translation agent has to
maintain the current amount of consumed/requested resources in
order to be able to calculate the correct amount to be put into
an outgoing message.
The translator maps each incoming RPP (resp. DCC) message into an
outgoing DCC (resp. RPP) message, and possibly establishes or updates
local state that is associated with the session. The translated
(i.e., outgoing) message is a function of the incoming message as
well as existing state that is associated with the current session.
Translation occurs on an attribute-by-attribute basis. Certain
attributes are translated without consideration of local per-session
state. Other attributes, namely those that are bound to a particular
session, require such consideration. The translation agent has to
identify the session (and possibly subsession) an incoming message
belongs to in order to consult the appropriate local per-session
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state.
Note that certain DCC attributes cannot be translated due to their
semantics not being present in RPP, and vice versa. This results in
the messages, in which these attributes occur, not being delivered to
their intended destination. In such cases it is desirable to inform
the originator about the failure and terminate the session.
In each scenario (i.e., RPP client / DCC AAA infrastructure and DCC
client / RPP AAA infrastructure), the translator operates in two
directions, namely RPP to DCC and vice versa. In the following
sections, the notation c->s means that the attribute in question may
occur only in the direction from the client to the server. The
notation s->c denotes the converse and the notation c<->s denotes
that the attribute may occur in messages that are directed in either
direction.
B.1. Session Identification
The translation agent has to keep per-session state in order to
perform its task. A session may be identified based on the RPP
identifier or the DCC session identifier. That is, the translation
agent should always maintain a pair of (RPP, DCC) session identifiers
and maintain the per-session state in association with that pair.
This per-session state must be addressable by either of these two
identifiers. Moreover, an RPP session identifier must uniquely
correspond to a DCC identifier. (If this holds, the converse also
holds.) Each subsession identifier within an RPP session must also
uniquely correspond to a subsession identifier within its
corresponding DCC session. (If this holds the converse also holds.)
B.2. Translation between RADIUS Prepaid and Diameter Credit Control
This section describes the translator in the "RPP client / DCC AAA
infrastructure" case. In other words, in this section it is assumed
that the client "talks" RPP and the AAA inftrastructure "talks" DCC.
The translator is assumed to sit somewhere in the middle and to
mediate between client and server.
For each RPP AVP (i.e., AVPs that are specified in the present
document), the transformation into a semantically equivalent DCC AVP
(if such an AVP exists), along with what per-session state the
translator has to create or consult, is described. For clarity of
exposition, each RPP AVP is addressed in a separate subsection.
Since in this scenario, the PPC is typically the initiator a session,
the focus is on the RPP AVPs.
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B.2.1. PPAC (c<->s)
A DCC client is assumed to always support Volume metering, Duration
metering, Resource metering, Pools, Rating groups, and Tariff
Switching. Thus, if a PPAQ that indicates any of the above is sent
client->server, the translator does the following: It lets message go
through but remembers what exactly the client supports. If the
server later requests (servier -> client direction) an unsupported
metering to be performed, send failure to server and cause the
session to be terminated at the client.
If a PPAC indicates support for multiple services (0x00000020), the
translator maps this onto a DCC Multiple-Services- Indicator AVP.
B.2.2. Service Termination Attribute (c->s)
The Diameter base protocol assumes that the client always supports
dynamic session termination. If this AVP is present, the translator
does not need to do anything, i.e., there exists no DCC AVP that this
AVP can be mapped to. If this AVP is absent, the message in which it
appears should either be discarded and originator should be informed
of a failure, or the message can be passed on (without this AVP being
mapped onto a DCC AVP). However, in the latter case, the translator
has to remember that the client does not support dynamic termination.
Thus, the translatior has to initiate the normal session termination
procedure with the client when (if) dynamic termination is later
initiated by the server.
B.2.3. Quota Identifier Attribute (c<->s)
When quota is allocated for the first time by the DCC server, the
translator has to create a QID AVP, as required by this
specification. The translator later uses a QID AVP that is sent in
the client-to-server direction in order to identify the corresponding
DCC session. The QID has to be saved in the translator's per session
state.
B.2.4. Volume Quota Attribute (c<->s)
If this AVP occurs in a message that is sent in the server-to-client
direction, it is translated into a Granted-Service-Unit AVP with an
embedded CC-Total-Octets AVP.
If this AVP occurs in a message that is sent in the client-to-server
direction, then it is translated into a Used-Service-Unit AVP with an
embedded CC-Total-Octets AVP. Note that only the difference between
current cumulative quota for the (sub)session and the quota in
incoming messages is indicated in the translated DCC message. Local
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state is updated with cumulative consumed resources.
Conversely, if the server grants quota using the DCC Granted-Service-
Unit AVP with an embedded CC-Total-Octets AVP, then the translation
agent must translate this into a Volume Quota Attribute. Again,
local state must be consulted so that the cumulative amount of octets
is indicated in the Volume Quota attribute.
B.2.5. Duration Quota Attribute (c<->s)
If this AVP occurs in a message that is sent in the server-to-client
direction, it is translated into a Granted-Service-Unit AVP with an
embedded CC-Time AVP.
If this AVP occurs in a message that is sent in the client-to-server
direction, then it is translated into a Used-Service-Unit AVP with an
embedded CC-Time AVP. Note that only the difference between current
cumulative quota for the (sub)session and the quota in incoming
messages is indicated in the translated DCC message. Local state is
updated with cumulative consumed resources (i.e., time).
Conversely, if the server grants quota using the DCC Granted-Service-
Unit AVP with an embedded CC-Time AVP, then the translation agent
must translate this into a Duration Quota attribute. Again, local
state must be consulted so that the cumulative amount of seconds is
indicated in the Duaration Quota attribute.
B.2.6. Resource Quota Attribute (c<->s)
If this AVP occurs in a message that is sent in the server-to-client
direction, it is translated into a Granted-Service-Unit AVP with an
embedded CC-Service-Specific-Units AVP.
If this AVP occurs in a message that is sent in the client-to-server
direction, then it is translated into a Used-Service-Unit AVP with an
embedded CC-Service-Specific-Units AVP. Note that only the
difference between current cumulative quota for the (sub)session and
the quota in incoming messages is indicated in the translated DCC
message. Local state is updated with cumulative consumed resources
(i.e., resources).
Conversely, if the server grants quota using the DCC Granted-Service-
Unit AVP with an embedded CC-Service-Specific-Units AVP, then the
translation agent must translate this into a Resource Quota
attribute. Again, local state must be consulted so that the
cumulative amount of resource units is indicated in the Resource
Quota attribute.
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Note that the "resource" type is application dependent. This means
that a DCC application unit corresponds to n RPP application units,
where n may be any real number. If n is not 1, then the RPP/DCC
translator must be aware of that and translate resource units
accordingly.
B.2.7. Value Digits Attribute (c<->s)
The encoding of this AVP is similar in RPP and DCC, and the value it
holds may have to be evaluated in conjunction with an acommpanying
"Exponent" AVP. It should be kept in mind that, in RPP the
cumulative amount of granted/consumed quota is typically encoded into
an AVP of this type, while in DCC only the difference from a previous
message.
B.2.8. Exponent Attribute (c<->s)
The encoding of this AVP is similar in RPP and DCC, and the value it
holds may have to be evaluated in conjunction with an acommpanying
"Value Digits" AVP. It should be kept in mind that, in RPP the
cumulative amount of granted/consumed quota is typically encoded into
a related "Value Digits" and "Exponent" AVP pair, while in DCC only
the difference from a previous message is encoded into such a pair.
B.2.9. Volume/Duration/Resource Threshold Attributes (s->c)
In DCC the concept of "threshold" does not exist. Instead, the DCC
client is assumed to ask for the replenishment of quota in good time.
In RPP, on the other hand, the server may optionally include a
threshold AVP, as an indication to the PPC about when to ask for
quota replenishment.
Thus, in this scenario, there is no need for the translator to ever
include a threshold attribute into the messages that it sends to the
PPC. If, however, there is a need for a threshold attribute to be
present in order to avoid a possible service provision
B.2.10. Update Reason Attribute (c->s)
The DCC AVP that is semantically closer to the Update Reason AVP than
any other AVP is the CC-Request-Type AVP. This AVP indicates whether
the message is which it appears is intended to indicate an "initial",
an "intermediate" or a "final interrogation". Morever, in case of
the session being terminated at the client, it indicates the reason
for this termination.
The following list lists the possible values of an "Update Reason"
attribute, along with corresponding values for the CC-Request-Type
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AVP.
o Pre-initialization: No action/value defined.
o Initial Request: Typically an "intial interrogation" is triggered
as a result of the reception of the message that contains this
Update Reason AVP. Hence, CC-Request-Type AVP indicates
"INITIAL_REQUEST".
o Threshold Reached: The reception of the message containing this
Update Reason AVP typically triggers an "intermediate
interrogation". Hence, CC-Request-Type AVP indicates
"UPDATE_REQUEST".
o Quota Reached: The reception of the message containing this Update
Reason AVP typically triggers an "intermediate interrogation".
Hence, CC-Request-Type AVP indicates "UPDATE_REQUEST".
o TITSU Approaching: The reception of the message containing this
Update Reason AVP typically triggers an "intermediate
interrogation". Hence, CC-Request-Type AVP indicates
"UPDATE_REQUEST".
o Remote Forced Disconnect: Reception of such an Update Reason
indicates that the client has terminated the session. The
corresponding value for the CC-Request-Type AVP is
"TERMINATION_REQUEST".
o Client Service Termination: Reception of such an Update Reason
indicates that the client has terminated the session. The
corresponding value for the CC-Request-Type AVP is
"TERMINATION_REQUEST".
o "Access Service" Terminated: Reception of such an Update Reason
indicates that the client has terminated the session. The
corresponding value for the CC-Request-Type AVP is
"TERMINATION_REQUEST".
o Service not established: Reception of such an Update Reason
indicates that the client has terminated the session. The
corresponding value for the CC-Request-Type AVP is
"TERMINATION_REQUEST".
o One-Time Charging: Such an Update Reason indicates that a one-time
charging event is initiated by the client. The corresponding
value for the CC-Request-Type AVP is "EVENT_REQUEST". Note that a
"Requested-Action: AVP MUST also be included in the outgoing DCC
message. Typically, this would be of the type "DIRECT_DEBITING",
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or "REFUND_ACCOUNT", depending on other AVPs present in the
message.
B.2.11. PrepaidServer Attribute (s<->c)
The PPC typically never sets the value of a PrepaidServer attribute.
Instead, it repeats those values that it receives from the AAA
infrastructure, in this scenario from the translator. This attribute
is therefore not used in a translation scenario. Nevertheless, the
translator must make sure that messages about the same RPP session
are forwarded to the same DCC server, throughout the whole session.
This may be easy to guarantee since the transport of Diameter is TCP.
B.2.12. Service-ID Attribute (s<->c)
The DCC equivalent of a RPP "Service-ID" AVP is the combination of
Service-Context-Id and Service-Identifier AVPs. The translator must
keep a static equivalence table of the RPP Service-ID and the
corresponding DCC combination in order to correctly translate an RPP
service identifier into DCC and back.
B.2.13. Rating-Group-ID Attribute (s<->c)
The DCC equivalent of a RPP "Rating-Group-ID" AVP is also called a
"Rating-Group-ID". Depending on the configuration, this AVP may
contain the same value on both the RPP and the DCC side of the
communication. If, however, static rating groups are configured
between the RCC client and the translator, and different rating
groups between the DCC server and the translator, then the translator
has to maintain a static translation table for the rating group
identifier. In any case, the translation of a rating group AVP, is
not a function of the translator's local per-session state.
B.2.14. Termination-Action Attribute (s->c)
The DCC equivalent of the "Termination-Action" AVP is called the
"Final-Unit-Action" AVP. In this scenario (RPP client and DCC AAA
infrastructure), a DCC "Final-Unit-Action" AVP is translated into a
"Termination-Action" AVP. The following list contains the possible
"Final-Unit-Action" values along with their "Termination-Action"
equivalent.
o TERMINATE (DCC): This value has a direct equivalent in RPP, also
called "Terminate".
o REDIRECT (DCC): If this value appears in a "Final-Unit-Action"
AVP, then a "Redirect-Server-Address" AVP must also appear in the
same DCC message. The translator translates these two AVPs into a
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"Termination-Action" with value "Redirect/Filter" and an
eqiovalent NAS-Filter-Rule attribute (specified in http://
www.ietf.org/internet-drafts/draft-ietf-radext-ieee802-00.txt).
o RESTRICT_ACCESS (DCC): If this value appears in a "Final-Unit-
Action" AVP, then a "Restriction-Filter-Rule" AVP must also appear
in the same DCC message. The translator translates these two AVPs
into a "Termination-Action" with value "Redirect/Filter" and an
eqiovalent Filter-ID attribute (specified in http://www.ietf.org/
internet-drafts/draft-ietf-radext-ieee802-00.txt).
o In the absence of a "Final-Unit-Action" AVP, the DCC server
assumes that the DCC client will ask for replenishment of quota at
some suitable time. In RPP, this is explicitly conveyed via a
"Termination-Action" AVP with the value "Request More Quota".
Thus, in the absence of a "Final-Unit-Action" AVP, the translator
in this scenario appends such an AVP into the outgoing RPP
message.
B.2.15. Pool-ID Attribute (s<->c)
The DCC equivalent of a RPP "Pool-ID" AVP is also called a "Pool-ID".
Typically, no translation needs to be done to the "Pool-ID"
attribute.
B.2.16. Multiplier Attribute (s<->c)
The multiplier attribute, which is a pair of "Value-Digits" and
"Exponent" AVPs, typically needs no translation, since the value it
carries (inside a "Value-Digits" and an "Exponent" AVP) represents
the rating of the service or rating group to which it refers, with
respect to abstract units. As such, the same multiplier value would
typically applyt be conveyed from a DCC server to an PPC, and vice
versa.
B.2.17. Requested-Action Attribute (c->s)
The "Requested Action" AVP can be directly translated into its DCC
equivalent, which carries the same name.
1. Balance Check (PCC): CHECK_BALANCE (DCC)
2. Price Enquiry (PCC): PRICE_ENQUIRY (DCC)
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B.2.18. Check-Balance-Result Attribute (s->c)
This attribute carries only a binary value. Hence, its translation
is straightforward.
B.2.19. Cost-Information Attribute (s->c)
This attribute consists of a Value-Digits AVP, an Exponent AVP, a
Currency Code AVP, and a Cost-Unit AVP. All these AVPs do likewise
exist in DCC, and carry identical semantics in the context of the
"Cost-Information" AVP. Thus, the translation of this attribute is
straightforward.
B.2.20. VolumeUsedAfterTariffSwitch attribute (c->s)
This attribute carries the amount of octets that were consumed after
a tariff change. It always appears in a message with an accompanying
PPAQ attribute in which the total amount of octets (i.e., those that
were consumed both before and after the tariff switch) is reported.
Thus, the translation agent can compute the amount of octets that
were consumed before the tariff change.
In DCC, the two amounts, i.e., the octets that were consumed before a
tariff change and those that were consumed afterwards, are reported
in separate Used-Service-Unit AVPs. The two Used-Service-Unit AVPs
have an embedded CC-Total-Octets AVP that indicates the appropriate
amount of octets. Furthermore, the Used-Service-Unit AVP that
carries the amount that was consumed before the tariff switch also
carries an embedded Tariff-Change-Usage AVP with the value
UNIT_BEFORE_TARIFF_CHANGE (0). Similarly, the Used-Service-Unit AVP
that carries the amount that was consumed after the tariff switch
also carries an embedded Tariff-Change-Usage AVP with the value
UNIT_AFTER_TARIFF_CHANGE (1).
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Authors' Addresses
Avi Lior
Independent
Email: avi.ietf@lior.org
Parviz Yegani
Juniper
Email: pyegani@juniper.net
Kuntal Chowdhury
Radio Mobile Access, Inc.
Email: kc@radiomobiles.com
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo 02600
Finland
Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
Andreas Pashalidis
K.U.Leuven, ESAT/SCD/COSIC
Kasteelpark Arenberg 10, bus 2446
Leuven-Heverlee B-3001
Belgium
Email: andreas.pashalidis@esat.kuleuven.be
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